To your points: I didn't talk about the influence of yield rates because at no point during my two years in admissions was a decision ever made on a kid based on whether or not we thought they'd matriculate to our school. This simply did not happen in my presence, so I didn't speak to it.
Note This is one of the problems I have with college admissions consultants. They charge kids an arm and leg to help them get into elite schools, but few if any of them actually ever admitted kids to elite schools. All they can do is look at the black box, see what goes in, what goes out, and then make educated guesses about why. That's not good enough for the prices they charge.
Unfortunately, most of the folks I know who have worked in admissions are so humbled by the process that they wouldn't think to sell kids on the idea that they could get them into an elite school. I tried it for about 3 weeks during grad school and just couldn't do it. It was too ridiculous. The kids that are going to get in are going to get in. The kids that won't, won't. I could take a big payday to inform kids that they will or won't be admitted, but no one wants that service. They want you to polish them into a winner, even if it's not the case.
So the bad information and the snake-oil salesmen dominate the conversation, folks like these people http://ivywise.com