Kalshi's record NFL weekend shows why bettors need to shop around

NFL parlays built Kalshi's biggest weekend ever. They were also priced higher than DraftKings and FanDuel.

Kalshi traded $2.46 billion on Sunday, September 13, and $2.43 billion the day before. These back-to-back single-day records topped a high the exchange had set only eight days earlier. Multi-leg combo contracts were 61% of the weekend's $4.89 billion in total volume, according to TickerTracker data published by The Event Horizon. Kalshi's Sports category, which is counted separately from combos, was 29% of the total.

Dallas against the New York Giants was the weekend's most-traded game at $113 million in standalone football volume.

Cheaper on straight bets, dearer on combos

Citizens analysts Jordan Bender and Isabelle Slavin tracked pregame moneyline and over/under prices at FanDuel, DraftKings, and Kalshi on the Friday afternoon before the slate, 28 data points in all. "Kalshi pricing was better than DraftKings and FanDuel in Week 1," they wrote in a Monday note to clients, putting Kalshi's implied vig at 3% below FanDuel and 4% below DraftKings.

Combos ran the other way. The pair averaged Kalshi's prices on the over and the favorite in every Week 1 game, using 14 data points, and calculated an implied vig of 23.8% against 22.0% at DraftKings and FanDuel. Their Kalshi figure is before transaction fees, and fees, spread, and depth all sit between a quoted price and what a trade actually costs.

That split is a line-shopping question rather than a platform one. In Week 1, the exchange priced straight bets better, and the sportsbooks priced parlays better. Our NFL odds comparison lists exchange prices alongside sportsbook lines.

Fees widen the combo gap rather than closing it

A sportsbook's parlay price already carries its margin. On Kalshi, the fee sits on top of the price paid, a difference in how prediction markets and sportsbooks make their money. The 1.8-point gap Bender and Slavin measured is a floor rather than a ceiling.

Kalshi's fees take a bigger percentage of your stake on lower-priced contracts. Its published fee schedule shows that buying 100 contracts at 10 cents costs $10 and incurs 63 cents in fees, or 6.3% of the money at risk. Buying 100 contracts at 50 cents costs $50 and incurs $1.75 in fees, or 3.5%. That makes fees particularly relevant when comparing longshot combos with sportsbook parlays. Our Kalshi fees guide breaks down the costs in full.

Volume is not handle, and combos are why

The $4.89 billion is notional volume, and it counts both sides of every trade. A longshot combo can change hands for a fraction of a cent and still register a full dollar of notional, which is why the parlay share of volume runs well ahead of the parlay share of money actually staked. The Event Horizon flags the same distinction.

The composition is the more useful number. Traders built 2.16 million combinations across 19.49 million legs over the two days, with a median of about six legs each. Combos of 11 legs or more accounted for 47% of parlay volume. NFL player props were 12% of Sunday's straight football trading and 44% of its football parlay legs.

The pull was sector-wide across the rest of the prediction market sites. DraftKings' DKeX, Crypto.com, Novig, and Underdog each posted their two biggest trading days over the weekend, with combos above 83% of Underdog's volume. Rothera, the one CFTC-regulated venue in the group without a parlay product, was the only one that did not set a record.

The question for bettors

For bettors, the significance is less about which venue won Week 1 and more about what the split says about where each kind of bet now belongs.

Adam Fiske, CEO of Cipher Sports Technology Group, parent company of Dimers, says the Week 1 numbers turn the price into two questions.

"For a couple of years, the pitch was simply that prediction markets offered better value than sportsbooks," Fiske said.

"Week 1 suggests it depends on what you're betting or trading. Kalshi offered better prices on single outcomes, while sportsbooks offered better prices on parlays.

"For bettors and traders, the takeaway is to shop around. Compare prices for the bet you want to place or the trade you want to make, rather than assume one platform always offers better value."

What to watch

Whether the share holds. Week 1 is the loudest week of the NFL calendar and draws traders who may not be back in October. If combos are still 61% of the mix in Week 6, parlays are the business rather than a September spike.

Whether the gap closes. Bender and Slavin noted that Kalshi's combo pricing was worse last season than it is now and said they are watching whether the combo market-making fee introduced in August moves spreads and vig for market makers. That is the number to check against the sportsbooks again in a month.

Trading on prediction markets carries real risk, and you can lose everything you put in. If it stops being fun, support is available here.

Disclosure: Dimers has a commercial relationship with Kalshi.