I honestly do not know why people are surprised by this. People who play sports (say football) have no issue driving kids to matches. People who goes to bars, sometimes buy a friend a beer.

In a internet community of 10-500 people, someone will have the spare 10$ for a domain name, and someone else will have a other spare 10$ for some server space. sometimes, its the same person. Server and domain names are not expensive, and is about the same cost of a few beers. If you spend hundred and hundred of hours on the site, work on the design and add new features to it, spending 20-30$ a month is basically a non-issue (just look at mmorpg players).

The problem arrives when those 200 people turn into 200k people, but then, the economy tend to change. Members fees, donations, t-shirts, and sponsorship tend to be the solutions in those situations. If you have a site for classic cars with 200k daily visitors, I doubt you will have a problem finding a sponsor, even if you have a no-ads policy. Heck, I wouldn't be surprised if a car seller would not happily sponsor such community, and then send some nice profession images of "nice looking cars, just by chance available to be bought".