In 2008 I was given 2 offers from a company: WFH or paid relocation to work in-office. I chose the former, which came with a 26% lower salary, and have been remote ever since. Just comparing the salaries in that case is a little disingenuous, however, since the relocation was from a low cost of living city to a high cost of living city.

A large impact on the extent to which WFH may need to come at a discount is specialization: If you're easily replaceable with an in-office worker, why would the company deal with remote? If you're not so easily replaceable, the company is more likely to be willing to work with you on your terms.

There's generally been a large disconnect between the job market in the tech sector and the rest of the economy, at least until a few years ago. There's now much more of a bifurcation within the tech job market, where rank-and-file and entry level software engineers are suffering while experienced and specialized software engineers may be doing better than ever. This plays into the RTO/WFH discussion because some people may not have the option to get their preference at any discount, or given either option in the first place.