I suspect the open-source nature is largely irrelevant. You'll want to list it on sideprojectors, flippa.com, etc. But $60/profit per month I expect you'd not

I suspect the open-source nature is largely irrelevant. You'll want to list it on sideprojectors, flippa.com, etc. But $60/profit per month I expect you'd not receive much more than $500 as an offer. You might prefer to shutter the service than see the main site go closed for that amount of money.