While doing research I came across Zuora (http://www.zuora.com) which is a SaaS based subscription billing system. It turns out that their product "solves" the whole pipeline (sales -> use -> billing -> accounting) but it is very very expensive.

So my question is, why? I am not at all trying to pick on Zuora. My guess is they have a fantastic product, but I am having trouble justifying the price. Isn't this just a simple rules engine that produces reports?

My guess is that I am falling into the classic blunder that "It's Trivial" (http://www.codinghorror.com/blog/2009/07/code-its-trivial.html). I was hoping someone in the community could enlightenment me on the pitfalls, before I go off and build it myself!