How much do you generate in terms of donations?

I have been toying with the idea of not going down an ad supported route as a business plan. Instead the idea would be to run the site purely off donations.

Ideally the donations would cover one full time dev and the running of the site.

Has anyone been successful with this model? I know Patreon has gotten big over the past while and, of course, Wikipedia gets > $50m in donations.

I think 5,000 paying donators/supporters at 3 USD each would be the minimum to make it viable. Is this crazy to be considering?