I would be careful making recommendations like these. 4G can hold one person on a "large" map? Not at all. That doesn't even make any sense. The map could have a 100000 block world border, and if there is only one person on there will only be a few hundred chunks loaded total regardless of where they are (unless you are including chunk loaders and that is a totally different issue). I have servers that only allocate 3G of ram and with 15-20 people doing very active builds it usually uses only about 2G and sits at a solid 20 TPS. To be honest, the only thing I have every had that caued the TPS to drop (even on packs with 130+ mods and 10 active players) was (1) Complex or rapid worldgen and (2) someone spewing 10s of thousands of items onto the ground from misconfigured builds.
As for the donation spiral, I may be in the minority here (I honestly have no idea) but the moment I log into a server and see anything about donations I just politely leave to go my merry way. I have 5 servers using different modpacks with 10s of concurrent players out of 100s who play and I couldn't imagine charging anyone for that. It is a hobby for me and I get a lot of enjoyment out of keeping it all up. I totally understand that not everyone has my expertise, resources or free time. I'm sure it costs me a little bit in electricity, but I already had the infrastructure in place to host it myself so that's what I do.
I guess what I'm trying to say is "hobbies cost money" and "businesses make money". Both are excellent pursuits. Just make sure you know which one you want to be in before you start so that you stil have fun with it. Life's too short to do something for long that frustrates you.
