It is funny.
Winning bettors do not get to place $500 dollar bets at William Hill or at Bet365 or at SportingBet or at Paddy Power or at Bwin. They have their bet limits cut to pennies/cents within a couple of months at most.
These are recreational books and the do not tolerate people consistently winning money from them.
Ergo you are betting these for much smaller amounts and/or you are losing your shirt.