Right now, there are 68 Tournaments on the men's annual calendar. Of these, all but the Grand Slams, Davis Cup (live rubbers) and the Olympic final are best-of-three matches. Incidentally, the remaining tournaments are divided into three levels, but even these levels have some gradation of prize money between them despite being nominally the same standard of tournament. As an example, a couple of weeks ago the men were playing tournaments in Mexico and Dubai, both of which were at the "500" level (based on ranking points given to the winner). Stan Wawrinka won in Dubai and got a shade over $510,000 dollars. Dominic Thiem (one to watch for the future, incidentally) won in Mexico and got less than $350,000.
In both cases there was a parallel women's tournament, although the one in Mexico was a lower-level tournament so can't really be used to compare. The winner of the women's tournament got less than Wawrinka did (although the runner-up and semi-finalists got more than their male counterparts); although again this is possibly not a totally fair comparison as the women's tournament is possibly best seen as a slightly lower tier again.
Because it's better to regard the winnings as prize money rather than pay, I don't think that pay considerations -- time spent on court, number of sets played, etc -- should come into it. Even ticket sales per match are a bit tricky things, as sometimes the ticket deals will be for a day's play or for two matches, or some such, and then of course a Djokovic v. Federer final is going to draw more interest in general than a Nishikori v. Cilic one.