If you're new to pricing consider reading this short free ebook on pricing written by the CEO of Redgate software: http://www.neildavidson.com/dontjustrollthedice.html. It will help you think through how to approach pricing your product.
Your pricing should be based on what economic value you deliver. Since that value will be different for different customers you should tier your pricing.
Figure out one or a handful of the key levers that drive that value. For example, in your case it might be number of their customers that are part of their loyalty program or the total transaction value tracked or something else. Someone with 1,000 customers tracked vs. 5,000 are going to be getting a different amount of value from you and ought to be paying accordingly.