Using Kalshi as a free fair-value check on MLB lines

Been running lines against Kalshi's prediction market pricing lately as a sanity check before placing anything. Kalshi trades game outcomes as pure yes/no contracts with no vig baked in the way a sportsbook price does, so it's a decent proxy for "what does the market actually think this team's win probability is" — then you can see how far a book's line has drifted from that.

Quick example from last night: Kalshi had Toronto/SF sitting at 52% implied. Vig-stripped, that's basically a coin flip with a slight lean. If a book's moneyline implies something meaningfully different from that, that gap is either the book's edge or their liability management — worth knowing before you bet into it, not after.

Not saying Kalshi is gospel (thin volume on some games, spreads widen late), but as a free cross-check against book lines it's underused. Anyone else watching this or just relying on standard line-shopping across books?

A sportsbooks lines are going to move based on where the money is moving it...... nothing to do with 'fair' value

@VicVega91

partly right — lines move on where the money is, not on some abstract "true" number. That's exactly why the gap matters. Kalshi isn't claiming to be "true" either. It's just a second market pricing the same outcome with no vig and no liability to manage. When a book's line and Kalshi diverge, that's not proof the book is wrong — it tells you why they might be off: lopsided public action, or the book's own edge baked in. Either way, that's a signal book-only line shopping doesn't give you. Shopping across books tells you who's cheapest. Checking against Kalshi tells you why books disagree in the first place.

interesting stuff