1. Post a range that is way too high or too low for some regions, which badly messes with expectations and can be very misleading to candidates, defeating the whole point of posting salary ranges in the first place.
2. Post a range that is so broad as to be meaningless (which is what some companies appear to be doing now). However this can also mislead candidates.
3. Omit the salary range entirely. This is obviously not ideal, but personally less information seems better than wrong information.
What do you do when posting international jobs? How has that worked?
So instead of saying "100-150k/yr", you could say something like "2-3 times the median income for the area where you live".