Presumably you can afford it if your income is that high. While there are arguments to be made that it shouldn't be means-based at all (it destigmatizes it, for one), it does seem to be working as intended.
It's not unreasonable for a plan that the government is always trying to chip away at for financial reasons. But a lot of people look at Medicare and think that it's essentially free which it decidedly is not for anyone with a current or recently high salary. (The add-ons cost a bit too but relatively not.)