Because of "I have been wondering if that is too much but I can afford it and I know this can be expensive to run."

Yes, $8/month is not a lot in the grand scheme of things. But I'm yet to see any more efficient and fair method for price discovery than having different commercial instances trying to acquire users through a straightforward business model where accounts are paid. I wrote a bit about that on https://raphael.lullis.net/community-is-not-enough/.

I am reasonably sure that I can have a profitable business on communick if I have enough people paying me ~$0.50/month, as long as all of the users pay me at least that much. More importantly, I am absolutely sure that our society and level of civil discourse would be better if we got rid of "ad-funded/freemium/donation-based" services, and instead we let market forces act and if we could vote with our wallets.

The way I see it, you shouldn't be paying $8/month to make up for the 15 freeloaders and your server admins shouldn't be dependent on your generosity to be able to continue providing the service. Everyone, without exception, should be paying just enough for the admins to feel like it's a worthy endeavor and willing to compete for your patronage and to improve their service. And because the service is built on free-software and has no strong lock-in, any improvement would quickly be shared and spread throughout all services.