For a $500 entry you would only need 50 players to get the $25K prize. That sounds kind of low so maybe the casino is keeping too big of a rake. Many tournaments say that the minimum is guaranteed based on entries. Also remember that in many tournaments the $25K (for example) is the TOTAL prizes awarded, not first place.

For $500 you could play a $1 JOB video poker machine for a week while generating enough comps to last a year. Needless to say I find slot tournaments boring at best.