There is two conditions:
1. You play that game with really bad players.
2. You play tight-aggressive with a bit bigger raises preflop.
And 5BB CAP is not so bad. If you play with 100BB effective stack, go allin and win 200BB hand paying 5BB rake you will end with paying 2.5% rake for that hand.
Lots of people fail to understand that the rake in their $5 cap game with lots of 30BB stacks might be harder to beat than $20 cap in a game where people initially buy in for 100BB, stacks fly around and at the end of the day there are plenty 500BB+ stacks. Not too long ago somebody asked about a highly raked game like that and such a game is obv. beatable.
High rake games also discourage people from playing who are break even(ish) in lower raked games. So there's a pretty good chance a game has 3 good and 6 bad players instead of 2 good, 5 break even to slight losing, 2 bad players you find in lots of US casino poker rooms.
It's beatable, they key thing though is you need most of your profits to come from 150BB+ pots. If you're winning a lot of 50-100BB pots in this game you're going to get destroyed by rake. There's no way it's profitable with shorter stacks.
As long as you're talking about NLHE, almost every rake is beatable, you just need to be good enough, opponents need to be bad enough (this is the most important part), and stacks need to be deep enough. Whether that's actually the case is another story. Almost all poker players severely overestimate their edge vs. the field.
At the 25/50 at the Venetian in Macau they have 5% capped at 5 BB. IME some of these games are beatable, but many are not.
