Prostitution is one of those cases where the price that most people would be willing to sell something for (and therefore by implication the loss in utility) is unusually large compared to the market price. So prostituting yourself would result in a net loss in utility at the point where you received the money. You may then be able to spend the money on EA to produce a net gain in utility, but you could produce a larger net gain by obtaining the money in a different way (that doesn't result in as big a loss of utility) and then spending it on EA in exactly the same way.

So it would only be a good idea to prostitute yourself for EA if you have no other way of obtaining money that doesn't reduce your utility by even more. If so, you have no business donating to EA at all.