It is an example of the fallacy of argument from personal incredulity.

No it's not. On the one hand you've provided no reason to think that it should be immoral to spend the money on yourself. On the other we have our moral intuitions which for most of us don't indicate that spending money on yourself is morally wrong. It's not as if you had any evidence or argument to suppose that we should donate any money. There's nothing to be incredulous of.

The link you've provided doesnt support what you are saying. It uses something "seeming" morally right as justification for examining claims that is is morally wrong, not as a moral counterargument in and of itself.

This is the first sentence on the link: "Another popular charge is that classic utilitarianism demands too much, because it requires us to do acts that are or should be moral options (neither obligatory nor forbidden)." And a sentence from further down. "But buying the shoes does not seem morally wrong. It might be morally better to give the money to charity, but such contributions seem supererogatory, that is, above and beyond the call of duty."