It’s worse than that. The salary factor isn’t how much graduates earn but how much more they earn than students with similar ACT/SAT scores. So, average students can do well if they get vocational training. This will almost always mean engineering and business programs will come out ahead of those that prepare students for advanced degrees or success in lower-compensated fields like teaching, social work, counseling.
This also explains why HYPSM still ranks highly, but well-regarded schools like duke, Vandy, Rice, NWU, UChicago (75? Really?) and JHU (92!!!) don’t fare as well. Those students have similar test scores to HYPSM, but HYPSM for a variety of reasons, places more graduates at Citadel, Blackrock, McKinsey, Deloitte, etc. If they used family income as a basis to judge how well the college boosted a graduate’s salary it would be a very different ranking.