Trading Costs Converge Amid Explosive Volume Growth
As combined monthly trading volumes on the top prediction markets surge past $53 billion, a new analysis reveals that base trading costs between the two leading rival platforms remain fiercely competitive. According to a recent breakdown by The Defiant, a standard 100-contract trade yields nearly identical taker profits on both Polymarket US and Kalshi.
The analysis demonstrates that a hypothetical position—buying at 40 cents and selling at 60 cents—produces almost exactly the same net profit for takers across both exchanges. However, the true cost of trading diverges when traders factor in resting orders and the specific funding methods used to capitalize accounts. For traders looking to optimize these margins, utilizing a prediction market calculator is becoming essential to account for these variable funding costs.
$53 Billion Market Faces State-Level Headwinds
This razor-thin margin in fee structures comes as both platforms experience unprecedented growth. According to Decrypt, combined monthly trading volume on Kalshi and Polymarket more than doubled from $26 billion in May to $53 billion in July, driven largely by sports betting contracts.
Yet, the intense economic competition in the Kalshi vs Polymarket rivalry is playing out against a backdrop of severe regulatory threats. Both platforms are currently fighting state-level crackdowns that threaten their lucrative sports and political markets. As reported by Cointelegraph, Utah Attorney General Derek Brown recently sued Kalshi and market maker Susquehanna, seeking to claw back up to $60 million in profits generated from 32,000 state residents since 2024. Utah officials petitioned a court to compel the companies to return the funds, with Brown labeling the operation a "public nuisance" causing "significant and substantial ongoing harm" to Utahns.
Kalshi spokesperson Jacki McGavick defended the platform's peer-to-peer fee structure and regulatory standing amid the lawsuits. "Our customers trade with each other and set the prices," McGavick stated, emphasizing that as a national derivatives market overseen by the CFTC, the platform answers to federal law rather than individual states. Meanwhile, Polymarket US is actively seeking preliminary and permanent injunctions against Ohio after the state demanded an immediate halt to its sports contracts and written confirmation of compliance by October 16.