[piltdownman]

If you earn over a certain amount in a year, and are categorised as a deriving your majority income from gambling in a 0% tax Territory (Austria, Australia, Belgium, Bulgaria, Canada, Czech Republic, Denmark, Finland, UK/Ireland etc...), you can offset the % charged as an expense.

FWIW, an exchange doesn't necessarily want a bunch of equally skilled players betting each other, they want a lopsided book on the bigger markets to attract domestic bookies and match-makers laying or staking across multiple platforms to leverage Matched betting discrepancies on promotions for new players etc...

//Players with a strong edge dramatically reduce the time before the losing players run out of money, meaning less commissions for the exchange.

Poker Players with a strong edge have a +ev Variance. Over 100 hands they're not guaranteed to be a winner. Over 10,000 hands they are.

YMMV massively in other sports, but for horse racing the big gamblers tend to only put down big money once or twice a year on maidens and trial-runners for Cheltenham or Grand National. They wouldn't touch a big festival other than for fun.