there are a couple ways you could value this. in terms of users, you could probably acquire users at $1 apiece, so 14,000 users = $14,000 + (new user value). not sure what their growth rate is since all we know is that they've acquired 14,000 in 18 months, but if we give them the benefit of the doubt and say they've grown by 2,000 users in the past month, we'll say we can acquire an extra 24,000 users in the next year assuming the buyer puts no effort into it, so that would be a value of about $38,000.

user acquisition doesn't seem to be the best way to value these guys, and there wouldn't be that much value for us, anyway, since we grow by 14,000 users about every 3 days.

however, since they're pulling in (a pretty astounding) $3.43/user/year (even the inactive ones), based on the $4k/month figure, they could bring in $130,286 this year. Multiply that number by 2 to be conservative, or 4 to be more ambitious, and you have a valuation anywhere from $250,000 to $500,000.

having said that, any potential buyer would need a lot more information before making that kind of decision, such as what their revenue growth looks like, what it would look like realistically projected into the future, etc.