Yes, it is.
Okay, since this is a serious question, I'll take a shot at answering it. First, let me repeat your question:
So why does Trump need contributions for his campaign? I thought that was supposed to be part of his appeal, that he was self-funding and could not be bought, being a billionaire
Trump never claimed he doesn't want or appreciate help funding his campaign; quite the opposite. He doesn't, however, sell influence or ownership of the Oval Office that too often comes with accepting contributions from special interest, large donor contributors. Money needed above the small dollar donations from his millions of supporters is on him.
It's one of the reasons he's frugal and gets the job done at a lower overall cost.

His supporters know this and are happy to help.