Do people really pay a percentage to other invoicing tools? I've been very happy with QuickBooks at £15/month and that's much more than an invoice generator. Even the smallest, £6/month one gets you invoicing as well as expense management.
Depends, I won't throw dirt around but the old invoicing software I used to use took a (albeit ridiculously small) percentage cut instead of a monthly fee, and the whole platform was entirely free forever.
We're working on our public billing API over at BillTo (https://bill.to). Our beta product currently allows you to integrate Stripe to bill customers within seconds, and we'll be opening up the API before Q2 for anyone to automate their billing with our backend.
Would love to chat and see how we can help with your specific use case.