The constant whine
So, the noise goes up again. Why can't women tennis players get as much money as men do?
Sure, people should get what the market pays.
The Grand Slams are in a monopsony situation. The players don't have substitute buyers (other tournaments) and the barriers to entry into the Grand Slam circuit are unbelievably high. Currently, it also seems like supply of players is fragmented and inelastic. Hence, theoretically the Grand SLams can offer any price that they want.
However, the Slams are in a fairly competitive product market (competing against many other sports and entertainment options), which will punish a sub-standard product severely. Hence, the demand curve for the best athletes is also pretty inelastic. That is where the challenge to the monopsony power comes in.
This demand side is probably the only point worth discussing in arguments for equal pay (and not the stupid men-work-harder argument). If the Grand Slams discriminate between men and women when the spectator's don't, we will go further away from an optimal situation and we'll see a correction (example, at the margin, women will refuse to sign up for the tournament and viewers will punish the Slams disproportionately). However, if viewers genuinely like men's tennis more, then it is optimal to pay men more.
On that note, I have read at various places that women's attendances and TV ratings are as high as men's, if not higher (another example, here). Is it?
I couldn't find any such evidence. Instead, all reports I found through a google search showed that men's ratings were higher (anywhere between 5 - 30%). Attendance at Men's tour is also higher, though I couldn't find the statistics for comparable tournaments. I wish I had access to this report to sort this out and calculate what the difference in pay should be.
At least from the evidence I have seen till now, a 5% difference seems justifiable.
Update: Pratyush has been collecting reports on this issue.