I don't know what the lower bound is, but a specific answer is "$97.67 per month" which is what I pay for a server in a rack in a data center that has been chug

I don't know what the lower bound is, but a specific answer is "$97.67 per month" which is what I pay for a server in a rack in a data center that has been chugging along, with an occasional drive failure, for the past 15 years that hosts a forum, a bunch of low traffic websites, and an email server. I also run a BBS on a Raspberry Pi that plays host to a few hundred DAU, that engage in chat, forums, a MUCK, and the occasional file transfer which runs on my home internet connection. I am sure someone will jump right in and tell me that I am doing it wrong and I can host everything on an AWS micro VPS for $4/month, but the amount that I pay is for my server. I also suspect someone will jump right in and tell me I am not allowed to host a server on my home internet connection.