Many things come into play with your question....Much depends on "where" the tournament is being played...."If" it is played on bar tables and the "players" pay quarters for the "matches"....money is generated just by pure virtue of the "tournament" being played. "If" it is played in a "pool room".....green fees....cover some of the cost of having "tournament tables" unavailable for rental while the tournament is taking place. As far as the actual percentage (%), there are no hard and fast rules....Certainly anything above 20% seems excessive. EXAMPLE: $25 entry fee ($5 going to green fee)....$50 entry fee ($10 going to the green fee) etc..etc.. Also the tournament operator SHOULD note in advertising "if" there is a green fee "included" or "in addition" to the entry fee. "Tournaments" are part of someone's "business" (Leagues, Bars, Tours, Pool Rooms etc..etc..). There has to be a reason and way for the "operator" to generate $$$. The "key" is to be transparent in your calculations, posting, advertising and pay-outs. Let's face it...."If" you are paying 25% of the field....that means 1/4 of your field is standing in front of your "tournament board" calculating your PAY-OUTS (to see if all the $$$...added or otherwise is REALLY there). I have seen tournament operators DESTROY tournaments because of "creative accounting" on prize money pay-outs. REMEMBER that "1/4" of the field looking at your tournament board are the BEST PLAYERS in your area (that's why your paying them)....."If" they feel they have not been paid correctly, they will NOT ATTEND future events and will make sure EVERYBODY knows WHY they are not attending....Do you want 25% of the field out there "*****ing and moaning" about your event???