I've read all your answers, some very interesting. I originally tried to sell my products on eBay before ITCH.IO and I have had very little results, even by supplying printed manuals, light-scribes CDs and home delivery. With "ITCH.IO" I'm found better,but, although I'm here by only 3 months, I have not had a great result yet. The ad technique is, perhaps, valid, but also, in my opinion, one must find the right audience.
Interesting the GameJolt site!