26岁的Leonidas Mastrokostas曾在FanDuel工作，从中发现了这一机会，随后独立运作，他表示自己每月通过在Kalshi上与散户对赌赚取七位数收入。FanDuel的母公司Flutter Entertainment同样积极参与，利用其定价专长在其他交易所进行组合投注的做市。根据各州数据，体育博彩公司在过关投注上每投注一美元可赚取19美分，而单注仅为6美分，显示组合投注的利润率远高于传统投注。
组合投注对普通投注者尤其危险，因为低概率的快速复合效应使人难以判断定价是否合理。Kalshi的组合投注平均隐含概率仅为9%，远低于非组合市场的43%。做市商透过报价请求（RFQ）机制在约一秒内报价竞争，随著竞争加剧，做市商必须开发独立的定价模型以获取优势，而非仅依赖博彩公司的赔率。精算师Buchalter指出，大多数散户完全不懂如何为这些产品定价，隐藏的相关性让公众容易产生错误判断。
Retail bettors are flocking to long-shot multi-leg combo wagers on prediction-market platforms such as Kalshi, creating a highly profitable niche for sophisticated algorithmic traders who take the opposite side. Combos now represent 36% of Kalshi's monthly trading volume and have become the fastest-growing product category since their introduction last September. However, ordinary customers have suffered badly, losing a net $294 million on Kalshi combos since the start of 2026, according to Bloomberg's analysis of taker trades.
Former FanDuel employee Leonidas Mastrokostas, 26, has capitalized on this dynamic by independently market-making combos on Kalshi, reportedly earning seven figures per month. FanDuel itself, through parent company Flutter Entertainment, has also begun making markets on other exchanges, leveraging its pricing expertise from traditional sportsbook parlays. State-level data shows sportsbooks retain 19 cents per dollar wagered on parlays versus just 6 cents on straight bets, underscoring how lucrative these bundled wagers are for those offering the odds.
Combo bets pose unique risks for retail participants because compounding low probabilities obscures fair pricing, and hidden correlations among same-game outcomes make accurate valuation exceptionally difficult. Market makers compete through a request-for-quotation mechanism, initially relying on sportsbook odds but increasingly developing proprietary models as competition intensifies. While proponents argue that market-maker competition gives retail bettors better prices than traditional sportsbooks, the exchanges face a sustainability challenge: customers who rapidly deplete their funds may abandon the platforms entirely. (Key numbers: 9, 43)