So? A payment processor is, in many ways, a utility. There's only so much innovation I need out of Stripe - they need to process payments for me. Done. If a competitor is cheaper, it's valid to go for them.
One other good example to show how good rocket internet is: Here is a french website: http://www.adopteunmec.com/ (you can translate it by "adoptaguy.com") And here come RI in Germany: http://www.shopaman.de/, looks familiar?
You need trust, competence and support.
They need to be good at everything they do. Usually you won't get that from clones.
Don't get me wrong, there are usually where a clone could be good, but the Samwer Brothers don't do it to be the best.
When shit hits the fan, you want to be sure that Stripe will step up - don't expect that from cheap clones.
Put simply, there are times when "the best" isn't necessary, for financial reasons. Particularly when we're talking about payment processors that are literally skimming a percentage of your profit.