Is that so? I used to think that house edge applies to all sports especially football. But what do we say about the changing odds when the game is on? Isn't that the sportsbook doing it so that they can have an edge?
Bookies can try keeping a spread and odds change based on the money inflow, but it's not like they have complete control over it.
Once the odds are published, it's the money that comes in that generates the movement, just as in every single market, the odds are adjusted that flow, despite that they can still lose pretty heavily on one bet, unlike casinos it's way harder to adjust those, and from he start of the bet there is no guarantee that anyone would bet on the losers.
Let's assume everyone betting on Real-Barca put their bets on Barcelona, despite the odds going to 1.01 as money kept piling there was nothing saving the bookie from the disaster.
This happens a lot in horse racing, you suddenly have a punter throwing 100k at a 10:1 horse, you can adjust the hell of the odds after it, since the whole pot isn't covering that it's just praying he got it wrong.