How do you know EA applicants aren’t rich enough to let the school decide how much they’ll pay for college? Suppose a rich kid wants to apply to a HYPSMC type “elite” private. None of HYPSMC offers an option to apply ED, so that’s off the table. Instead the rich kids have a choice of either applying EA/REA or RD. One common approach is to apply EA/REA to their first choice among the group (REA prevents them from applying to peers for which they are likely to lose as cross admit). The overwhelming majority or rich kids are deferred/rejected to their EA/REA first choice, then they apply RD to a variety of lower choices, matches, safeties, etc; so they appear in both the EA/REA round and the RD round.
This is exactly what the the sample from previously posted Harvard lawsuit data suit showed. The bulk of Harvard applicants in both the REA and RD rounds were composed of wealthy kids, but there were also a significant portion of not wealthy kids in both REA and RD rounds. For example, there was only a small 2% difference in rate of kids who were low enough income to apply using a fee waiver among applicants in the REA and RD pools. More information about differences in composition of the 2 groups is at http://samv91khoyt2i553a2t1s05i-wpengine.netdna-ssl.com/wp-content/uploads/2018/06/Doc-421-134-February-2013-Report.pdf .
If you mean the non-HYP Ivies that offer ED, they don’t offer EA/REA – only ED and RD, so you don’t have any EA group. However, it’s a similar idea . A common approach is to apply ED to their first choice. The overwhelming majority or rich kids are rejected to their ED first choice, then apply RD to a variety of lower choices, matches, safeties, etc.
ED is also not just composed of full pay kids. For example, a comparison of the Dartmouth class of 2025 admitted under ED and full class is below. Both groups had a significant portion of kids who were not full pay.
Dartmouth ED Admits – 58% applied for FA, Average FA grant = $62k, 18% Pell eligible
Dartmouth Full Class – 50% qualify for FA, Average FA grant = $61k, 17% Pell eligible
It’s important if you believe that there are large differences in the composition in the early and regular round. MIT had approximate the same admit rate for their early and regular rounds, so if there are large differences in composition of applicants in the 2 application rounds, it suggests that those differences in composition are likely to have little impact in chance of admission at MIT.