Honestly speaking scripters hardly receive a decent share from their work and not to be a douchebag but you should always read the script thread and ask for a review of how the script works right now.. If you're just going in store and buying it without checking out who the writer is, how often a script is updated, how long does he take to fix bugs then honestly.. you're asking for it.
You have to understand that we don't sign any written agreement when putting a script on SDN, we just send a request providing the requested information and it's then deemed worthy by @Alek.
Yes there are, for example kOgres by Alek requires you to go to his website, send payment via PayPal and then receive a serial code for his script