I wonder what sort of person is aware enough of DDoS attacks to want to buy one, savvy enough to find where to buy one, yet dumb enough to pay with PayPal. Or accept PayPal if you ran such a service. Given, it says the people running it were 16-24 and adolescent hubris knows no bounds... Maybe the customers were the same general age as the owners?
Isn't almost any online payment method trivially trackable? Bitcoin (and most other cryptocoins) needs a bit of effort to grovel the public transaction history, and XMR does things that supposedly make that not really work at all, but other than that...
Any source? Can't find anything.