I looked it up, and we were required to complete form I-864 "Affidavit of Support Under Section 213A of the INA". My wife, her grandmother, and her grandfather all needed to complete one, and when considered together, prove that they earned 125% of the HHS poverty guidelines. As my wife didn't have provable income (we were moving together), we needed to dig into their social security income and complete the forms. I remember feeling sad that I needed to ask for such personal information from them.

My salary in the UK was many multiples of this guideline, but _earning potential_ is not considered. Pragmatism is not really a service offered by USCIS, it's too political. To be on-topic: this move will disincentivize smart but not-yet-wealthy people from immigrating to the "land of opportunity". It was already harder than it had to be.