A 1989 Upper Deck Buy Back Ken Griffey Jr. is up on eBay. You can find it here. The bidding was at $1625.00 at the time of this post. There is also another fixed price auction on ebay that's priced at $4895.00. You can find that here.
This is a great card that I would love to own but I can't imagine paying that kind of price for it. You could buy so many Griffey signed items, including game used equipment for that kind of price. I'm pretty sure one of these already sold in the range of $4000.00 but I couldn't find a completed auction for it on eBay.
One thing I'll say, Upper Deck sure knows how to create a buzz. I can't think of a better item to promote their 20th Anniversary than a signed version of the best card they've ever produced. If you collected in the late 80's and early 90's, you know that this was probably the top card of that era.