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To me it seems like it's not necessarily budgeting issue but natural greed kicking in. I'm sure imgur people are not tightening their belts over this.
The problem I see is that once you get even to the scale of a 10th of size of imgur your hosting bills (storage + bandwidth) will cross into the 10s of thousands per month, which would require you to be in the top 1% of Patreon users. I don't think you'd find people lining up to donate for such a service, especially given there are so many copycats.
On the other hand, I think Imgur also pushed way more traffic upon itself by trying to make itself into another social media site. Like, if it just stayed an image host it probably could have stayed more niche and wouldn't have had thousands of casual internet users scrolling through images all day at work.
There are quite a lot of examples in the past (all the way to the Roman empire) of rich people spending their money on community projects just because they wanted some things to exist, not to make even more money.