yes you are right. but i would look at the full package. say the expat gets the equivalent of 200k in all, including all benefits like housing and kids education. given the higher tax bracket he's in, and the fact that he "loses out" to locals who get many forms of subsidies (eg hdb), i would say his net income is comparable to a local family with husband and wife each getting 80k.
further, given the general lifestyle an expat leads (locals are extremely frugal in comparison), i would expect his savings to be comparable to a local husband & wife each making 60k.
of cos there are expats out there who really live like kings. but these are the ones getting at least 500k. i don't think there are many of them.