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The flaw in the equal-pay argument is to think that players are (a) "paid" at all -- it's prize money, not a salary, and (b) to think of sets as the important unit. They are not. The unit that matters is only the match. Raducanu has won the same number of matches as tonight's men's Slam winner. Three more, in fact.
If sets were the unit of pay, then prize money should also be made non-equal between men who win in straights, as opposed to those who come through an actual five-setter. But, of course, that argument will never gain traction, because it's stupid. It's equally wrong, then, to reward certain people more money just because they can play a hypothetically longer match, whether they do or not.
Now, having said that, I'd not mind seeing five-setter matches between women. It's happened before, there's no physical barrier. Arguably the only thing missing from tonight's final was more of it, it was so high-quality and I'm sure many would have loved to see the players battling out for at least another set. One revamp that I think is worth considering for slams, especially since scheduling is probably one reason why matches are being made shorter across the board, would be to have first-week matches all reduced to best-of-three, and second-week matches (4R and later) all extended to best-of-five. That way, you address the scheduling problem in the first week, when you have to fit 200-odd matches in across four days (even ignoring the doubles), but also keep the dynamic longer matches that have the potential to ebb and flow, and indeed expand it. In terms of quality, some of the matches in the women's draw, especially through Fernandez's run, were among the most thrilling I've seen in a long time.