Besides CDCK (the company behind Discourse), there are other companies specializing in Discourse hosting, with different price ranges.
As Jagster said, “do you have ability to host by yourself”?
Self-hosting will ask technical skills, and taking care of security/backups by yourself.
It will be considerably less expensive than managed hosting.
I own a decently active forum. It costs about 300$ a year (hosting, emails, domain name, CDN, backups), and is 100% funded by users’ donations.
The donations have been working very well for a few years now, even if it required sometimes several months until fees are met.
I recently set a real-time donations progress bar on the forum and it was a huge 
incentive for members to donate. Instead of waiting months fo reach the servers’ annual fees, it only took a few days this year.
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