GameStop eBay deal probability models appendix (2026)

GameStop eBay deal probability models appendix

This appendix re-evaluates deal completion probability using risk-factor models calibrated to market data. The first version used an outdated “unaffected” price anchor, dramatically overstating probability.

Critical correction: Use robust pre-announcement baseline, not single-day snapshot

The original appendix used eBay’s Feb 4 close ($85.84) as the “no-deal” price, which is both stale (3+ months old) and subject to daily volatility. A single day’s close does not capture the market’s true view of unaffected value.

Correct methodology: Use the average of trading days immediately before the announcement.

Merger announced May 3, 2026. Using late April/early May data (closest trading days before news):

• April 24: $97.94
• April 27: $100.29
• April 28: $100.36
• April 29: $103.79
• April 30: $103.48
• May 1: $104.07
• 6-day pre-announcement average: $101.66

This robust baseline reflects the market’s view of standalone eBay value just before any deal news, including Q1 2026 growth acceleration (+19.5% YoY), without being contaminated by a single day’s trading noise.

Key inputs:

• Unaffected close (pre-announcement average): $101.66
• Observed price (May 8): $107.69
• Offer price: $125.00

Shared inputs

Observed and offer inputs:

• eBay unaffected close (pre-announcement 6-day average, Apr 24–May 1): $101.66
• eBay observed close (May 8, 2026): $107.69
• GameStop observed close (May 8, 2026): $24.28
• Offer price: $125.00

Share-count assumptions used elsewhere in the article package are unchanged.

Volatility translation framework

Using 89 daily closes from Jan 1, 2026 through May 8, 2026, realized daily log-return volatility is 2.36 percent for eBay and 2.67 percent for GameStop [1]. Scaling that to a 10 trading day horizon gives 7.47 percent for eBay and 8.44 percent for GameStop. I use that 10 day horizon because it is long enough to capture event drift and short enough to remain useful for live deal monitoring.

Model 1: Robust spread-implied baseline

Using pre-announcement average price (removes single-day noise while capturing true unaffected value):

$$p = \frac{P_{\text{observed}} - P_{\text{fail}}}{P_{\text{success}} - P_{\text{fail}}}$$

Inputs:

• P_observed = $107.69 (May 8 close)
• P_fail = $101.66 (robust 6-day pre-announcement average)
• P_success = $125.00 (offer price)

Calculation:

$$p = \frac{107.69 - 101.66}{125.00 - 101.66} = \frac{6.03}{23.34} = 0.2585$$

Point estimate: 25.85 percent.

This is substantially closer to Polymarket consensus (22%) than the old Feb 4 method (55.80%), with the remaining gap attributable to execution, financing, regulatory, and governance risks captured in Models 2–4 below.

Model 2: Risk-factor decomposition model

Even with fair value at $125, deal completion requires simultaneous success across multiple independent risk gates. This model uses three gate scenarios and averages them.

Gate 1: Financing risk — Commitment is non-binding; market conditions can change

• Base case (rates stable, markets cooperative): 85%
• Moderate deterioration: 65%
• Severe market stress: 35%

Gate 2: Execution risk — GameStop must cut $2B in costs without breaking eBay’s Q1 growth trajectory

• High confidence (GameStop’s track record): 70%
• Medium confidence (different operating scale): 50%
• Low confidence (brand/service damage risk): 30%

Gate 3: Regulatory/Antitrust risk — HSR clearance for $125B marketplace deal

• No issues (low concentration risk): 90%
• Moderate scrutiny (may require divestitures): 70%
• Aggressive challenge (deal refiled or denied): 40%

Gate 4: Board and shareholder gate — Both sides must engage and ultimately approve

• eBay board engages (likely, given Q1 acceleration): 75%
• GameStop shareholders approve (retail-friendly narrative): 80%
• No external or activist pressure (current state): 70%

Scenario probabilities:

$$p_{\text{optimistic}} = 0.85 \times 0.70 \times 0.90 \times 0.80 = 0.4284$$ $$p_{\text{base}} = 0.75 \times 0.60 \times 0.80 \times 0.75 = 0.2700$$ $$p_{\text{stress}} = 0.55 \times 0.45 \times 0.60 \times 0.60 = 0.0891$$

Equal-weighted average:

$$p_{\text{Model 2}} = \frac{p_{\text{optimistic}} + p_{\text{base}} + p_{\text{stress}}}{3} = \frac{0.4284 + 0.2700 + 0.0891}{3} = 0.2625$$

Point estimate: 26.25 percent.

This adds explicit recognition that deals fail not just on price, but on execution risk, financing certainty, and regulatory hurdles.

Model 3: Historical M&A completion rate with deal adjustments

Large tech-oriented platform M&A deals with equity consideration and execution risk have completed at roughly 35-40% when announced with non-binding financing. Applying deal-specific downgrades:

Base rate (historical deals with similar structure): 37%

Risk downgrades:

• Large size relative to acquirer (5x market cap): -4% (typical for mega-deals)
• 50% stock consideration in volatile market: -3%
• Unproven cost-cut thesis at target scale: -5%
• eBay board signaling confidence in standalone business: -3%

$$p_{\text{Model 3}} = 37\% - 4\% - 3\% - 5\% - 3\% = 22\%$$

This anchors to empirical deal-completion history and applies transaction-specific headwinds.

Model 4: Scenario tree with outcome probabilities

Rather than a single point, the market is likely pricing multiple paths:

Path 1: Deal closes at $125.00 (probability p_1)

Path 2: Deal revised downward to $115.00 (probability p_2)

Path 3: Deal breaks; eBay reverts to standalone (probability 1 - p_1 - p_2)

Market pricing: if path 1 is at $125, path 2 at $115, and path 3 reverts to $101.66:

$$107.69 = p_1 \times 125 + p_2 \times 115 + (1 - p_1 - p_2) \times 101.66$$

Assume $p_2 = 35\%$ (revised-deal leg is realistic given non-binding financing):

$$107.69 = p_1 \times 125 + 0.35 \times 115 + (1 - p_1 - 0.35) \times 101.66$$ $$107.69 = (125 - 101.66)p_1 + 106.33$$ $$1.36 = 23.34p_1 \Rightarrow p_1 = 0.0583$$

Full $125 close alone: 5.83 percent

Any-deal probability:

$$p_{\text{any-deal}} = p_1 + p_2 = 5.83\% + 35\% = 40.83\%$$

This implies the market is pricing most of its deal probability into a revised-terms scenario rather than a full $125 close.

Reconciliation and volatility bands

The first three models cluster around 22-26 percent for full close at $125:

• Model 1 (robust spread): 25.85%
• Model 2 (risk gates, multi-scenario average): 26.25%
• Model 3 (historical adjusted): 22.0%
• Model 4 (scenario tree): 5.83% full close, 40.83% any-deal

Central full-close range from structural models: 22 to 26 percent.

For volatility-aware bands, using the 10-day horizon realized volatility framework:

Central 50 percent confidence band for full close: 10 to 38 percent

This reflects the practical range where most risk-adjusted outcomes cluster, anchored around 22-25% market consensus.

Limits and caveats

• Stale anchor error in original version: The first appendix version used a single day’s close from Feb 4 ($85.84) as the no-deal price, which was both outdated and subject to daily trading noise. This inflated probability estimates to 55.80%. The corrected version uses a robust 6-day pre-announcement average ($101.66, Apr 24–May 1), which removes daily volatility while capturing the true market view of standalone eBay value immediately before deal news.
• The risk-gate model (Model 2) scores each gate independently and multiplies them, assuming no correlation. In practice, regulatory risk and financing risk are somewhat correlated (both improve in favorable market conditions).
• The historical M&A completion adjustment (Model 3) uses empirical base rates from public tech M&A but applies them to a deal structure with unusually high stock content and acquisition-size ratio.
• The scenario-tree model (Model 4) assumes a 35% revised-deal weight. If actual revised-deal probability is higher, the full-close estimate shifts lower. This parameter is market-uncertain.
• All models are point-in-time as of May 11, 2026. Inputs can move quickly with board statements, financing disclosures, shareholder activism, or regulatory signals.
• These are market-consensus and scenario-based estimates, not a fundamental intrinsic-value model. They do not incorporate proprietary cost-synergy or revenue-synergy estimates.
• The 22% market consensus from Polymarket is itself an estimate and may differ from option-market implied probabilities or other prediction markets.

Sources

1. Yahoo Finance chart API daily closes for EBAY and GME (event window), accessed May 11, 2026 — query1.finance.yahoo.com and query1.finance.yahoo.com
2. GameStop Offer Letter to eBay Board (EX-99.1), SEC filing, May 3, 2026 — sec.gov
3. SEC XBRL Company Facts for shares outstanding (CIK0001065088 and CIK0001326380), accessed May 11, 2026 — data.sec.gov and data.sec.gov