Assuming the players drafted are all FBS-scholarship players except for 1 or 2 each year, then we have 253 or 254 of 10,200 (85 scholarship players on 120 teams). This means 2.48-2.49% of the FBS-scholarship players go to the NFL.
Let's assume that 95% of the NFL-drafted players are scholarship players on a top-30 school. I.e., 242-243 players from the top 30 schools are drafted. This equates to 9.49-9.53% being drafted. (242 or 243 divided by 2,550 (85 times 30))
A risk-averse person would pick a school based on more than their likelihood of being drafted. Less than 10% isn't something to hang your hat on.
Delving into the perceived value presents a picture of what a reasonable recruit would see as the payoff of attending one of these top 30 schools.
With the NFL average salary being $1.9M and an average career lasting 3.5 years, that's an expected $6.65M payoff for those making it to the NFL. This means that hs recruits at top 30 programs see an expected $631-634K payout on their football ability.
If you use median salaries over average salaries (which I think are more realistic), then the expected payout for their football ability is $256-257K.
Either way you dice it, it's a big chunk of money to anyone coming from modest means.
You can merge these numbers with whiskey's expect ROI for schools to provide a more accurate picture for each school. It's also possible to calculate the expected NFL payout for players going to each school. Some schools turn into NFL factory mills every now and then (Miami in late 90s/early 00s, then USC, now Alabama). My only concern is that NFL potential has less to do with the school, than the individual.