To make a tournament +ev I have to be better than X% of the players?

[mrjetguy]

I know this is a bad question that has no definitive answer, but I think it is interesting to consider. Obviously we have to consider everything in the longrun to make this worthwhile. But say I want to play in a tournament with a 10% rake (ie: $20+2), what percent of the players do I have to be better than to make the tournament profitable to play in? Beyond that, say I was in the top 10% or top 1%, what kind of ROI would I then expect.

I know so much of this depends on playing styles and other factors, but I think some sort of general math based answers can be had. I would just like to hear some thoughts about this. This is more something that I was thinking about and found interesting than something I have to know so that I can make decisions about what tournaments to play in.