Elliot Rodgers described himself as a "sophisticated gentlemen". That is, he meet the conventional stereotypes of masculinity. He lived at a rich neighbourhood, had a good car and payed attention to his looks. Since he meet those conventional stereotypes, he *feel* he should be getting sex. He had done *his part*, but girls weren't doing *their part*. Elliot Rodger wasn't a geek or a nerd. At no pint did he showed interest on nerdy things.
You might want to consider that what led him to believe that he was owed sex, wand made him angry was not that he didn't meet the traditional image of masculinity, but that he did, and wan't getting the supposed "reward" for doing it. Now, the "reward" is sex/a girlfriend. But girls are their own person and didn't respond as he had been told by many people (including you repeating that it is money what made men interesting to women) and he become frustrated.
Take a look at the women you call "themcells" or incels. They usually have "followed the rules" and "done everything well". They would list all the things that they have done and are as the reasons they should have a "good men" (whatever it is acording them) and yet they are not getting "the reward". They might have even sacrificed things to do "their part". That is why they feel aggravated.
If you pay attention, it is the same pattern. They are [insert stereotype] and have done *everything well* (what society tell you to do) yet they are single. If they have fullfilled their part of the deal (go to college, get a job, buy a house, etc), why aren't they getting a partner?
And of course the reason is that it was a lie from the begining. Nothing would guarantee you a partner/sex. Life is unfair and you need to make the most of what you have and deal with the rest the best you can. But instead being angry with the people who promised him a girlfriend if he behaved certain way, he was with the girls who didn't buy into the lie and the other men who also realized that things doesn't work that way.