I'm not entirely sure if sports-betting markets are wholly made of liquidity just from the pockets of the bettors. I believe the betting company must place their own money on one side of the bet or the other to keep the market balanced if there isn't enough money from the users to take the other side of the bet.
Isn't it the case that these sites don't have to be balanced and most of them aren't? that if there is, for example, $1 million in customer funds for a win and $100,000 for a loss, then we simply have a total of $1.1 million in bets, 50k takes the casino as its fee, 1.05 million remains, so if our team wins for each $1 in bet, we get 1.05 $ back, and if we bet on the team loss and we win we get $10.5 back for each $1 in bet?
So if an arbitrageur comes in and bets $100,000 on teamX lose, it just changes the win/loss statistics and doesn't change how much the casino earns? So it changes the distribution of winnings between bettors and makes money from it?
Am I wrong here?
Plus because professional arbers always win, that means they are a net-loss to the betting company because they could consistently withdraw money out of the betting company's pool of liquidity.
As I understand sports betting, the arbitrageur's profits are constant and certain, as you wrote, but they do not reduce the casino's profits but, for example, reduce the winnings of those betting on X by $1,000, increase the winnings of those betting on Y by 990$ and they get $10 out of it for themselves.