Odds and prices
What are the odds in gambling?
Odds are the chance of an outcome. In a casino they are also the payout attached to it, and those two are never the same number.
A single number on a roulette wheel hits once in thirty seven spins. It pays thirty five to one. That missing bit is where every casino on earth makes its money.
True odds and paid odds
True odds are counted, not decided. A single-zero wheel has thirty seven pockets, so a straight-up number is 36 to 1 against. Nobody argues with that.
Paid odds are set by the operator. Thirty five to one on a bet that should pay thirty six leaves 2.70% of everything staked behind, which is the house edge on that wheel and it does not care what you bet on.
Double zero adds a pocket and keeps the same payout. Same game, same table, and the cost of playing it nearly doubles to 5.26%. That is the single biggest decision available at a roulette table and it happens before the first spin.
What the number costs an hour
Turn the edge into cash and it stops being abstract. C$5 a spin, sixty spins an hour on a live wheel, is C$300 through the table. Single zero takes about eight dollars of that. Double zero takes sixteen.
Slots are quicker and the maths is the same shape. A 96% title takes four cents a dollar staked, and a phone deals two hundred spins in twenty minutes. Pace matters more than the percentage on the label.
Sports is a different animal
In a casino the odds are fixed by the rules of the game. In a sportsbook they are a guess with a margin on top, and different books guess differently.
That is the only place in gambling where shopping around changes the maths in your favour, which is why anybody serious about betting keeps two or three apps installed rather than one.