So, when picking up these "1 of 1"s on eBay, use the judgement that you should be using on all of your purchases. Buy the card if you like it--don't get caught up in the 1 of 1 madness. Know that the card is rare, is unique and is something that you'll enjoy. Keep things in perspective and you'll be fine.
This "1 of 1" Watch will continue in perpetuity to try and determine how many of these sketch cards were produced.