Ask HN: For how much should I sell my side project?

Hi HN,

I have a Saas side project that I'd like to sell, but not sure about the price.

It's solo and bootstrapped. I work on it for 2-3 hours per month, answering emails, no other work is required.

It has 70 paying users and 500 total. Profit is around $4000 monthly. What would you say?