[DrVanNostrin]

It depends on how big the rake is and how good the players are. If the rake is large and the players are mediocre his EV could easily be < 0.

I'm somewhat unclear on what comparison you're interested in. Do you want to know whether it's wise to stake good players so they may sit a game with you?

It depends how much of the player you get. The larger the amount you have the more likely you should be to put him in. If the rake is 1BB/hour the aveage player's WR is -1BB/hour. If you replace an average player with a player who's WR is 1BB/hour it will cost other 9 players at the table 2BB. Each of those 9 nine players is likely to lose 2/9 BB/hour as a result of the switch. If you have 10% of this player you'll lose 2/9 BB/hour when he enters the game and will only get 0.1BB/hour back from staking (you'll lose money on staking). If you had 50% of him you'd still lose 2/9 BB/hour but you'd get 0.5BB/hour back from staking (you'd make money on staking).

This isn't exactly right for a couple of reasons:
1) You'll lose less than the average player as a result of the switch because you know more about the staked player than others do.
2) If the staked player's true win rate was 1BB/hour it will be less than 1BB/hour given that you're in the game (I'm assuming you're also a winning player).
3) It's also dependant on seating. Players who sit near the staked player will suffer a little more as a result of the switch. Those who sit on the opposite side of the table will suffer a little less.