It's always been possible to set up your own payment system using your website, some custom server-side scripts, and the AJAX plugin (or preferably a custom plugin). However it doesn't seem to have been a popular option, probably because we attract non-programmer users and this requires server programming and setting up a payment system like Paypal, which you absolutely have to get right (or you could get hacked and lose money). Still, if you have a friend who's good with web technology, you could try setting something up together.
Thanks for your info, there are payment systems with PHP in Codecanyon :)