Service pricing

If you can offer a service to, theoretically, 100s or 1000s of customers for <$500 per month in recurring fixed costs, which start small and grow relatively proportional to customer base, plus $40/hour labor (possibly less, considering offshoring) where onboarding each customer requires some 5-50 hours of fairly simple analysis and HTML/CSS work, what kind of pricing structure/levels would you look at?

Initial investment upfront is a few dozen hours of my time in development, setup, etc., and a few hundred bucks out of my pocket. Ongoing investment of my time is hopefully mostly administrative/accounting and not development -- expect to contract out all ongoing development tasks -- and on the order of 20 hours/month or less.

This would be a base service with additional a la carte value-add options available, and potentially professional services offerings as well. Again, like onboarding, proserv would be contracted out.