I can imagine that quite a few would do this. If not at $4,600 I would guess the floor on something like this would probably be 2-3K. If you have the resources and you know that your chances are already good, why not? I would bet that you could also write this off too depending on your tax situation.
Would I pay for this? Probably not. Am I in a position to apply for a job at Amazon with a high likelihood of success, probably not.