26歲的Leonidas Mastrokostas曾在FanDuel工作，從中發現了這一機會，隨後獨立運作，他表示自己每月通過在Kalshi上與散戶對賭賺取七位數收入。FanDuel的母公司Flutter Entertainment同樣積極參與，利用其定價專長在其他交易所進行組合投注的做市。根據各州數據，體育博彩公司在過關投注上每投注一美元可賺取19美分，而單注僅為6美分，顯示組合投注的利潤率遠高於傳統投注。
組合投注對普通投注者尤其危險，因為低概率的快速複合效應使人難以判斷定價是否合理。Kalshi的組合投注平均隱含概率僅為9%，遠低於非組合市場的43%。做市商透過報價請求（RFQ）機制在約一秒內報價競爭，隨著競爭加劇，做市商必須開發獨立的定價模型以獲取優勢，而非僅依賴博彩公司的賠率。精算師Buchalter指出，大多數散戶完全不懂如何為這些產品定價，隱藏的相關性讓公眾容易產生錯誤判斷。
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)