Although it's an almost guaranteed profit, there are few problems with arbitrage betting (aka arbing)!
Usually, it's hard to find an opportunity like the one you mentioned in OP because of the difference between the odds.
Second, supposing you find one, you will need a huge bankroll to make a good profit not to mention that most casinos will limit your account after few wins.
Then and most importantly, many casinos consider arbing illegal and may ban your account if they find out about it.
I'm replying to an old post, but it's relevant.
Plus OP said,
If you had a 20k bankroll you could make $1054 in a day betting these games. Then you would have to withdrawal all the money, wait for it to deposit in your bank and then re add to the sites. (or if you're lucky, half the bets will win on each site so you don't need to reconcile on each)
But how much of these opportunties does an arber actually have? Everyone would be doing it if it was truly "easy money", and if there are enough opportunties to be taken.
Because logically, if there are more and more people arbing in sports-betting, then there would be less and less opportunties because the odds would become more and more efficient.