There likely is some sort of market for commercial instances, but it's not me.
The same 5€/month that you are spending on the instance you are on could be helping you and 9 other people. Network effects matter. If you can bring 9 other people, you'd accelerating the rate of adoption of social networks based on open platforms. The people you will be bringing will have someone that can help them with the initial questions. They will be less likely to give up on it because they already have some kind of support network. If they really like what they find and if they find themselves willing to support it and get their own contract, they will find "it's $10/year for a single account or $5/month for 10-account contracts" more affordable/more straightforward than "pay whatever you want, but the social pressure is to pay 5€/month just for yourself".
I totally understand that if you already on an instance that you are happy, you already have some form of emotional attachment to it. But perhaps consider that your 5€/month could have an even bigger if employed on a commercial instance.
It's doing that on the instance I'm on; the instance has 20k users and about 800 contributors.
It also means that non-paying users don't have any social capital at stake. They can come, create issues for the moderators and at worst they would get banned. Someone that comes directly through your invitation is less likely to cause any type of issue and if they do it also gives more information for moderators about the best course of action.
It also means that if the server gets an influx of new users and double in size, you would either and they would have to rely either on a corresponding increase in contributors on a bigger donation from the existing ones. My commercial instance can only grow in proportion to the number of people that have already committed to pay. This makes it easier to plan and manage its growth.
