like many others, I hosted my own for a variety of reasons.

• I like to tinker
• this was a chance to do a lot of tinkering and get in on the "ground-floor" of something I think has a lot of potential
• it gives me a bit more control over the experience, which is helpful when trying to get friends/family to give Lemmy a chance.

As for the cost, I have several VPS's which cost ~$40/year, so the cost is basically negligible.