Lots of Product Hunt products are free, how do their makers earn?

I think a lot of creators are sharing their side-hustles while they're still in the product validation stage, which means the product maturity hasn't reached that threshold where you either have enough volume to monetize from ads, or enough value to monetize from subscriptions / freemium offerings. I'm not sure about everyone else, but my projects have mostly been solo experiments that I build for the sheer pleasure of building them in my free time, so my expenses are low (Azure PaaS costs me like $30/mo).