>I fail to see why this cannot co-exist alongside the Stripe alternative library.
It certainly can, anyone is more than welcome to pay for something done by open source software available for free.
>Surely if you're a business of any merit
Just because you're a business doesn't mean you should pay for things that you can do cheaper.
The point is that a decent web developer could recreate that form in 20 minutes with jquery.payment and a little bit of CSS, so why should you pay $300 for the same thing?