Are there any other SaaS alternatives to Chargify?

I was planning on implementing it into my app next week but I'm having doubts now with the price. There is no entry level option any more. For an app that is prerevenue, the up to 50 for free account was very compelling.

Now I'm required to pay $99 upfront regardless.

I may write my own as well. There's quite a few rails frameworks.