> We're talking remote, you can't mix remote and on-site in the same conversation.
You must consider both because, for now at least, people's BATNA is affected by local opportunities as well as remote ones.
> The BATNA of both is the same, because they're competing in the same global market.
The BATNA is different. The SF-based engineer can choose from a remote job or one in SF. The Delhi-based engineer can choose from a remote job or one in Delhi.
If the BATNA for both were the same, then you wouldn't be able to hire an engineer in Delhi for less than 80k USD (or whatever today's entry level engineer salary is in SF). But you can. This proves the BATNA is not the same.
We might want the BATNA to be the same. But today it is not. As a result, market conditions don't require companies to use the same pay grades everywhere.
When I lived in China, I worked for two different FANG companies (in Beijing and Shanghai). In both cases, the compensation bands for folks in China wasn't the same as those in the US West Coast. My total compensation was lower than I would have accepted had I been based in the US. But it was reasonable compared with the other options available to me without needing to move out of China. So neither company had an incentive to pay me more.