1) How many people transfer to rather than from the Europe or India office? I'd wager that it's mostly in one direction, which is towards the higher wages.

2) Are RSU grants are adjusted downwards after the transfer? I believe the answer is no. Which means that the total package is not decreasing significantly until cliff.

3) What's the pre-existing financial situation for folks that move towards a lower CoL area? If you've already made a significant enough amount of earnings in the US that you could survive off of them in your destination, the base salary is going to matter a lot less.

4) Is there lateral incentivization in terms of trajectory? If you get to start a new office in a different country (or head a new team or something along those lines), the clout you develop long term may be enough to balance out the temporary salary loss, as when you return back to your origin country, you could have leveled up substantially and retain your level. You're effectively engaging in arbitrage here.

Suffice to say, I don't have a great answer, but I will note that this is a pretty specific exception, enough to make me repeat that platitude that "it's the exception that proves the rule."