I'm curious to learn more about how you decided on your pricing. I've used Marketo for a few years now, it's an absolute PITA to set up simple campaigns and I've often thought of creating an alternative simply out of frustration.
I wanted it to be high enough that I could actually make money with it (i.e. not $15/month), but low enough to be accessible to people at my marketing level a year ago.
This is the product I wish I had when selling my books.
I really liked Visual Website Optimizer's pricing, so I used that as a model.