What a bet is actually worth
Every other idea here is built on one number: the price a bet would carry if nobody took a cut.
A sportsbook's price is not its opinion of the odds. It is its opinion plus a margin, and you cannot tell whether a bet is good until you take the margin back out. That removal is called devigging, and it is the single most useful thing to understand about betting markets.
A coin flip, priced by a book
- Heads
- -110 (implied 52.4%)
- Tails
- -110 (implied 52.4%)
- Implied total
- 104.8% — not 100%
- The extra 4.8%
- the hold: the book's cut
- Fair price, margin removed
- 50% / 50%, or +100 each side
Both sides look like losing bets because both sides ARE losing bets at -110. The market's real view is an even coin flip.
Where the fair number comes from
Not every book is equally informed. A handful — Pinnacle, Circa, the exchanges — take large bets from people who are right often enough to matter, and they move their prices when those people bet. Those books effectively discover the price; the recreational books mostly follow. TrueEdge weights them accordingly, strips the margin, and the result is the fair probability every screen measures against.
Why this makes the rest simple
Once you have a fair price, everything else is a comparison. A book paying more than fair is positive EV. Two books straddling fair far enough are an arbitrage. Two lines either side of fair are a middle. They are not four separate skills — they are four consequences of the same number.