No, the point is that it would be CHEAPER to buy or download this watermarked music because the record company wouldn't need to worry so much about piracy. If you are paying to download, they automatically know your PayPal ID and email address or some comparable identifier, and it doesn't cost you anything extra. If you are buying a physical CD at the record store and you want to pay cash, you pay full price but get a rebate when you send in the card with your name and address.
Databases are cheap to maintain now. My 80GB hard drive could easily handle all the record purchases in the USA for a month.
I'm not saying this is the right way to go, just making the point that it's technically reasonable to implement. I wish the record companies would wake up and realize they could do a lot better than this with a different business model, but this would at least be better than what they have. It's a bad situation now because of the "moral hazard" -- a certain type of unethical and illegal activity has become quite a bit easier to get away with.
I also wish that the artists would wake up and realize they don't have to idiotically sign away their rights with the same boilerplate contract language that has been used for decades.