Thanks! This is a really good questions to ask, especially given what happened to Couchsurfing.
I think one often underestimates just how cheap it can be to run a well designed and built site. We estimate that once we get to a reasonable number of users (where our servers aren’t just idle all the time), it should take comfortably under 5 cents per user per year to operate the servers. This is similar to what Trustroots reports, see post and stats (1-2k EUR for ~50k users).
This means that if one in a hundred users donate $5 per year, we’ll easily cover these costs. Or compared to Couchsurfing’s >$2 per month, this is less than a 500th of that! We feel that given the additional fact that we’re not a for-profit company, we’ll easily find people who are willing to contribute at this level!
Finally, some of us on the core team have decided to pay for the costs of the site until it picks up to a point where we have a substantial number of users (and where it’s polished enough that we feel okay asking people to contribute financially).