There's no other reason why men's sexual market value should be highest at this point, other than money. A late 30's man will usually look worse than a man in his 20's, so it can't be looks. So logically it has to be money. The extra money due to you being further along in your career means that a man finally has enough money to pay women for sex - either in some relationship arrangement where the man exchanges resources for a woman's companionship and vagina, or by directly paying hookers/escorts for sex.

Read between the lines and this is what TRP is getting at. Men are at their peak SMV because they can finally pay for sex by that point (they couldn't when they were younger because they were broke college students or in low paid entry level jobs).

Of course the minority of Chads were always high SMV regardless of how much money they had, but you don't need to come to TRP if you are a Chad.

TRP = The Red Pill, SMV = sexual market value (for anyone who is unfamiliar, although I'm sure you're all familiar)