Prediction Market Arbitrage: Hidden Costs, Fees, and the Real Math

The idea sounds beautiful: buy "Yes" on one platform for $0.40, buy "No" on another for $0.55, and collect $1.00 for a total outlay of $0.95. Five percent risk-free.

In practice, three layers of costs, several non-obvious risks, and different resolution rules across platforms stand between you and those 5%.

Three Layers of Costs

1. Platform Trading Fees

The key trap: many DEX platforms use dynamic fees that depend on event probability.

2. Network Gas Fees

3. Cross-Chain Bridges

Bridge fees: $1–5 per transfer + percentage. Time: 1–15 minutes (spread may close while you wait).

Three Critical Risks

1. Slippage

AMM worsens your price on large orders due to thin liquidity.

2. Resolution Risk — Where 90% of Arbitrageurs Burn

Same event, different platforms, different resolution rules and data sources. Your positions can lose on both sides simultaneously.

3. Timing Lag

No atomic cross-chain execution. Second leg may execute after the spread closes.

Minimum Spread for Break-Even

Profitable arbitrage realistically starts at 7–10% spreads.

Premarket.me — Aggregator for Arbitrage

Manually monitoring spreads across five platforms is impractical. Premarket.me solves this: it's a prediction market aggregator with a unified API that combines data from Polymarket, Limitless, Predict.fun and other platforms.

The key endpoint — /api/arbitrage — returns pre-calculated pairs: where to buy "Yes", where to buy "No", total cost, profit %, APR adjusted for time to expiry, and liquidity depth in USD.

Open-Source Arbitrage Bot

A ready-made Go arbitrage bot built on the Premarket API: suenot/premarket-arbitrage-bot.

Scanner (Premarket API) → Filter (profit/APR/depth) → Display → Executor (Polymarket CLOB)

The bot polls /api/arbitrage, filters pairs by configurable thresholds (MIN_PROFIT_PCT, MIN_APR, MIN_DEPTH_USD), and optionally executes trades via Polymarket CLOB with EIP-712 signing. Default mode: DRY_RUN=true (monitoring only).

Links

• 🌐 Polymarket · Limitless · Predict.fun · Opinion · Kalshi
• 🌐 Premarket.me: premarket.me · API Docs
• 💻 Arbitrage Bot: suenot/premarket-arbitrage-bot

Conclusion

Prediction market arbitrage is not "free money." It's systematic work with three layers of costs, cross-chain logistics, and resolution risk that can wipe out both legs of a trade. Minimum spread for break-even is 5%; for profit — 7–10%.

But the key insight: mechanical arbitrage alone is not enough. The real edge comes from building AI agent analytics around each specific bet: real-time news monitoring, tracking social signals, analyzing on-chain activity of large players, and correlating with macro events. The spread between platforms is a symptom; the cause is information asymmetry. The winner is the one who understands that event probability has shifted — not the one who clicks the button fastest.

Pre-funding wallets, maker orders, and API automation are table stakes. The real edge is in the analytical layer on top of market data.