National Bank Open: Marta Kostyuk vs Iga Swiatek

Platform comparison

Market context

Marta Kostyuk’s match with Iga Swiatek at the National Bank Open is priced by the market as a live underdog spot, with the crowd-implied **44%** sitting below a true coin flip but not far from it. That makes sense against the matchup history: Swiatek has led the head-to-head in most recent public records, including a 4-1 overall edge on one tracker and a 3-0 lead on others before Kostyuk’s 2026 French Open win narrowed the gap in that sample set.[2][3][4][13]

For traders comparing platforms, Polymarket’s probability view is easier to read at a glance, while Kalshi, Betfair and Smarkets typically express the same view as decimal odds or back/lay prices, which can make small moves look larger or smaller depending on vig and spread. The key practical difference on this match is that exchange-style books may show a tighter or looser price depending on commission and liquidity, whereas a KYC-gated venue can exclude some users entirely; that matters if the number drifts after line-ups or scheduling news rather than after a completed result.

The main catalysts are straightforward: the match has already been listed for 9 August in Toronto, and any change to start time, court allocation, or withdrawal before first serve can move the price quickly; if the match is not played, or is delayed beyond seven days without a winner, the market resolves 50-50 under the rules given. Recent score and scheduling pages show the pairing is on the current tournament slate, so traders will be watching the draw sheet, order of play, and any late fitness updates on either player rather than expecting a long news cycle.[10][6]

Sources: 1 · 2 · 3 · 4 · 5

Methodology

This page compares National Bank Open: Marta Kostyuk vs Iga Swiatek specifically across Polymarket, Kalshi, Betfair Exchange and Smarkets. The live probability is the Polymarket mid; the comparison columns summarise each venue's fee structure, KYC, settlement currency and payment rails. Every CTA routes to Robinhood Prediction Markets, which mirrors the Polymarket order book at 0% fees.

Resolution & payout

Settlement is the biggest difference between the four platforms: Polymarket on-chain in USDC (instant), Kalshi USD via CFTC (T+1), Betfair and Smarkets in local currency via bank withdrawal (T+1 to T+3). On-chain settlement clears in minutes — the fastest payout path of the four.

FAQ

Polymarket vs Kalshi — which is better?

Depends on your location. Kalshi is CFTC-regulated, US-only with full KYC. Polymarket is global, on-chain, no KYC up to $1,500. Polymarket has ~10x higher liquidity but higher regulatory risk.

What does Polymarket cost vs Kalshi?

Polymarket: 0% fees, only Polygon network costs (~$0.01/trade). Kalshi: up to 7% per trade plus spread. For high-frequency traders, Polymarket is dramatically cheaper.

Is Betfair a Polymarket alternative?

Only partially. Betfair Exchange is UK-focused with a sports-betting emphasis; they have politics markets but with thinner liquidity than Polymarket. Settlement in GBP/EUR, 2-5% commission on winnings.

What about Smarkets as an alternative?

Smarkets is a UK betting exchange with a lower default commission (2%) than Betfair. Liquidity on political markets is below Polymarket, comparable to Kalshi. Geo-blocked in many jurisdictions.

Which platform is accessible globally?

Polymarket is geo-blocked in the US/UK/EU. Kalshi is US-only. Betfair and Smarkets are UK-restricted. Robinhood Prediction Markets has a different geo footprint and routes to Polymarket's order book at 0% fees.