You can attribute its rousing success to the plethora of autographed rookie cards or the short-printed non-rookie cards that seemingly were inserted at a rate of one every other hobby pack.
And it doesnt hurt that the current Beckett Baseball price guide reflects hoards of up arrows next to the values of the vast majority of the sets autographed rookie cards.
This set also boasts some exclusive autographed rookie cards of players such as Washington Nationals phenoms Ian Desmond, which has been consistently moving anywhere between $60-75 a piece, as well as low-numbered rookie graphs of Mitch Einertson, Matt Tuiasosopo and Matt Bush.
SP Prospects gaining popularity may also be attributed to the highly condition-sensitive silver borders and easily scratched band-aid autograph stickers affixed to the front of every autographed card.
Since its release last November, sealed hobby boxes of SP Prospects have jumped to over $100 per box and seem to have plenty of room to move up even further, thanks to the generous insertion ratio of five autographs and two USA Baseball game-jersey cards per 24-pack box.
This product has the potential to be the next 2002 Bowman Chrome Draft Picks & Prospects, the mother of all baseball rookie card products.
A few of the hot autographed rookie cards in this set include Colin Balester, Michael Rozier, Eric Campbell, Jason Jones, Chris Nelson and the aforementioned Tuiasosopo and Einertson.
Remember, the SP Prospects autograph program stacks up right next to the Bowman Draft Picks & Prospects Gold and Red Refractors as the most highly sought-after rookie cards commemorating the 2004 June draft.
Its quite possible that sealed hobby boxes of SP Prospects could reach the $150-175 level if one or two rookies break out in during the first few weeks of 2005.

