Pretty sure this is demonstrably false. There are large spreadsheets out there documenting H1B wages at FAANG type companies and they are almost universally less than the equivalent US Citizen wages.
FAANG companies are not hiring H1-B's because it's cheaper. I have been a hiring manager at a couple of FAANG companies, and I can tell you it's just not something we cared about.
The only thing I cared about was finding the most qualified people for the team. I had headcount to fill, and it wasn't like that headcount had one salary band marked "For Citizens" and another marked "For H1-Bs". The compensation systems at FAANGs are for the most part formulaic.
If FAANG want cheap engineering labor they outsource and use contractors, simple as. And it's those companies - the Infosys and Wipros of the world - that are arguably are the biggest abusers of H1-B.
However, curious -- do these include stock grants, etc? I wonder if the posted numbers are only salary and not TC?
* It's base alone - no bonus, no stock
* It's base at the time you get on the visa - so mine was two years and some 80k out of date near the end
* My employer at the time used a standard letter for the four or so of us so we all have the same base listed but I know we didn't have the same base. It looks like it was the lowest value. Presumably they just kept the thing that was working.