Her points seem kind of rational in a pop-psychology way at first blush, but after thinking about it, it really just doesn't work that way at all.
Making sex a market metaphor makes you take on a lot of assumptions right up front just to make the metaphor work. Not everything is an economy. Trying to treat every aspect of life as an economical construct and explain the world using market forces is how you wind up with things like everything the US Government has done the last 30 years. It's a flawed premise and produces flawed conclusions.
For clarity, I want to stress that I'm not addressing sex as a service - the sex industry is a whole other thing that's ouside the scope of this conversation. I'm talking about regular, plain ol' homemade sex, a non-compensated activity that people do on their own time for fun and sometimes babies.
Sex is not a market commodity any more than running, or building a sand castle, or beating a video game. It's an activity, not an object you can trade on a market. You can't buy a can of sex. There's no finite quantity of it either, so the idea of market value is patently absurd - there's never more or less of it, it's value never changes. And thinking of it in supply and demand terms requires making some other pretty drastic assumptions about it anyway - dividing people up into 'producers' and 'consumers,' for one. Dr. Walsh seems to have presumed women to be producers of sex, and men to be consumers of it. On what grounds?
Listen: no one controls the supply of sex. There's no supply to control. Women don't have some limit they hit where that's it, they're done making sex, can't make any more. Men don't either. It's not about whether it's more available or less - fact is, it's not any more or less available than it was 100 years ago, or 500, or 5000.
And buried in the lecture there's that idea again, that really bad idea that so many people can't seem to get rid of, that sex is something you can go out and earn, something that makes men motivated, without it they'll lose ambition and it will be very sad for them.
This is a bad, wrong, stupid idea. Why this is a bad idea has been covered pretty thoroughly by several people on the first page of this thread. I'll just say this part again: it doesn't matter whether it's sex or taking a walk or having a water balloon fight, getting to do an activity with another person is not about supply and demand, it's not about availability, it's not about how badly it's needed or how hard they've worked for it or what they've been told about how it should be. It's about if both parties want to. Thinking of it like a commodity you can invest in and get a return from is going to lead to a bad time for everyone.