I can't believe how many people are belittling this idea or strawmanning it as a couple of dollars or $5. What the page is getting at is if you can get a few customers to actually commit real money, then you've got an actionable idea on your hands. This is so much better than any wishy-washy "that's a good idea" or "I'd buy that". This is a full fledged, "Here's my money, I am buying this right now." sort of decision.