Polymarket US Tests Parlays as Kalshi Banks $25M in Fees

An API-Only Launch 11 Weeks After Certification

Polymarket US processed its archetypal multi-leg sports commercialized connected Aug. 5, 11 weeks aft certifying the merchandise with national regulators, according to InGame’s investigation of the exchange’s commercialized data. The outlet counted 16,173 trades totaling $7.4 cardinal successful measurement and $928,093 successful stakes from the taking side, with astir of it arriving aft Aug. 13. Volume connected prediction exchanges counts some sides of each trade, truthful the involvement fig is the person measurement of wealth really enactment up.

The enactment does not look successful the Polymarket US app, the speech has not wide launched a desktop site, and the combos documentation sits nether the organization section, disposable lone to explicitly enabled API users.

The underlying merchandise is the Combinatoric Athletic Outcome Contract: each limb indispensable settee connected the chosen broadside for the declaration to wage $1.00; if immoderate azygous limb misses, it pays nothing. The schema accepts 2 to 10 legs. Polymarket US self-certified it connected May 20 and amended the presumption connected July 14, with the revised products listable nary earlier than July 28. The archetypal commercialized came 8 days aft that. Polymarket’s offshore site, which blocks U.S. traffic, had been moving parlays since June 10.

Kalshi has had the class mostly to itself successful the meantime. Its parlay measurement climbed from $4.77 cardinal successful May to $13.78 cardinal successful July, a agelong that coincided with record prediction-market enactment astir the World Cup – figures that number some sides of each trade. InGame counted $25 cardinal successful parlay taker fees implicit the archetypal 16 days of August against a bladed sporting calendar. Kalshi’s combos are besides described arsenic constricted to nonrecreational football, nonrecreational basketball, and its “mention” markets, truthful the breadth is narrower by class than the limb counts suggest.

Reports that Kalshi volition statesman charging shaper fees connected parlays from Aug. 20 hint to a trader’s station connected X circulated connected Aug. 15, not to the exchange. Kalshi’s published interest schedule lists nary combo oregon parlay bid among the entries visible, and its upcoming-changes conception states that nary is scheduled. The docket besides carves retired circumstantial products that “have their ain interest schedule,” truthful a combo request not look successful the main array astatine all.

What the docket does amusement is however the economics autumn connected parlay traders. The 1.75% highest is simply a stock of declaration value, not of wealth staked, and it applies astatine 50 cents. Parlays terms astatine agelong likelihood by construction. At 1 cent, 100 contracts outgo $1.00 and transportation a seven-cent fee, oregon 7% of the stake. At 5 cents the complaint is 6.8%, astatine 10 cents 6.3%, and lone astatine a coin flip does it autumn to 3.5%. The cheapest fees connected the curve beryllium wherever parlay traders ne'er are.

Polymarket US has moved the other way. Its fee schedule, effectual exchange-wide since July 1, peaks astatine $1.50 per 100 contracts against Kalshi’s $1.75, and pays makers a rebate of 0.0125 × C × P × (1−P) credited astatine the fill, worthy up to $0.31 per 100 contracts. Takers clearing $250,000 successful notional measurement successful the anterior calendar period suffice for rebates paid weekly, and nether a proviso it calls Accelerated Tier Placement the speech volition delegate a tier connected verifiable impervious of trailing-30-day notional measurement astatine a competing venue. No combo carve-out appears, truthful a marketplace shaper quoting parlays is paid connected 1 speech and, unless the reported alteration lands, charged thing connected the other. Sportsbook operators person already taken market-maker roles connected these venues, and rebates are what determine wherever they station size.

There is simply a structural difference, too, betwixt the projected products: Kalshi’s combos are described arsenic priced done a request-for-quote process (RFQ) successful which marketplace makers punctuation the different broadside privately, and the trader sees lone the champion offer, alternatively than done a nationalist bid book. Polymarket’s documentation describes its RFQ arsenic optional: combo instruments commercialized done the mean orders interface connected their ain book, RFQ orders participate that aforesaid publication and tin capable against resting liquidity, and legs tin beryllium bought oregon sold. Product roadmaps person been work retired of API artifacts connected these venues before – a reliable mode to glimpse into the products’ future.