eBay has always been an excellent way to get the cards I want, in my opinion. I've bought several cards over the last few years and have yet to have any problems with any of the various sellers and the cards have been in great shape when the show up in the mail.
Since I started the Super Script collection, eBay has been a huge part of it. Of the five that I currently own, three of them are from eBay. I also have two more on the way as I'm typing this. There is definitely no shortage of Super Scripts on eBay, the only problem is they are all newer, most commonly 09-10 cards lately. I've been luck with the 99-00's though, except for the three that got away from me in the waning moments of the auctions.
I've paid as little as $1.04 for a single Super Script, but I've seen one end up going for close to $60, and the rest are all over the place. These cards are in fact serial numbered out of only 25 and are probably appealing to a certain group of collectors.
I can see many of these cards going to player specific collectors though. There are probably a few others like me, trying to build an extremely difficult set, but I can't say that for sure because I've never seen anyone claiming so.