Also the slider seems to be capped out at some really low number (like 30 new customers a month or something?)... not sure if I'm doing something wrong?
The sliders are only one possible solution to visualizing the rate of growth per price tier. Most other things I've tried involve math fiddling that I haven't managed to translate well to a user experience.
Open to suggestions or examples if you have ideas!
Early on you have an idea of what sort of traffic you're able to generate and a likely conversion rate, and therefore estimate a sign up rate using real(ish) numbers. It's only the growth beyond that that you're really guessing at.
You may just want a text box with a gross # of new customers/month based on what you think you can bring in, and then have the slider work on top of that, in effect creating an adjustable polynomial function for growth? Just spitballing here...