Mine's a small instance and runs on my existing infrastructure, so my only real cost (aside from a crazy amount of unpaid time and stress) is the domain name which is about $20/year.
If I moved it to dedicated infrastructure, I've estimated it would cost me about $65/mo for just the backend, UI, and database services (to maintain the same level of performance, anyway. Could probably host it for less and take a performance hit). Object storage for pict-rs would probably be around $10/mo since I force it to use webp and have a 512 KB limit for user uploads.
Those numbers may be a little high, but they're based on my existing VPS provider which has amazing SLAs and uptime.
What would be the reason to move it to a dedicated infrastructure, you not needing your existing infrastructure?
Yeah, that, or if I decide one day I don't want to deal with my own hardware anymore. I've got a hybrid cloud infrastructure currently, and most of the heavy services (DB mostly) run on my own hardware for cost/performance reasons (and I have fiber, so might as well use it lol)
For me it's zero. In addition to reusing existing hardware, I have a subsidized internet connection that I reuse to connect my instance, and even the domain name is free.
Of course I also have fewer users - excluding me, zero.