If you really want to find out if targeting these users to maximise profits is harmful or not, I think it's a good idea to ask these spenders, perhaps have them take a survey. If you don't want that, I'm pretty sure there's research out there on gaming and spending habits that can shed some light on the question.
[Edit: I see that you sell through iTunes connect, and I don't know if Apple permits you to have anonymous user surveys in you app. Even then, I'd guess that you wouldn't risk your highest paying customers reconsidering their gaming habits by asking them uncomfortable questions in a survey. Given that, I would think actively looking for published research papers would be a good idea.]