Holy grails of the modern card world... It's not an easy thing to describe, really.
There's a woman in England who produces decks made by hand at about 50 per design, each one with a different artistic theme. They rarely sell for less than three figures.
Robinson's Fed52 decks are more of the real Holy Grail with his collection, because they were the first and, in the eyes of some, the best. In particular, the black unbranded Reserve Note deck was exceptionally rare - USPC shorted the print run by accident, leaving Jackson himself with not more than a handful that weren't sold to backers. In general, because they were his first, because he wasn't a well-known artist at the time, his Fed52 decks will likely always carry a premium price tag above his other projects, relative to the initial cost of purchase. His later projects, at least in terms of relative increase in value, are less likely to be worth as much, and his project with USPC for a $4 deck is highly unlikely to get too costly, considering the quantity that were produced and the low price tag they were offered at, though they do make for a great, cheap way to own a Robinson deck.
There are other modern decks that are worth a pretty penny - but that should make absolutely no difference to you, if you're a true collector rather than a speculator. A collector buys what makes them happy, while a speculator buy whatever they think will be sellable in the future for a profit, be it near or far future. It could be the rarest deck around, or it could be that cheap Chinese knockoff from the dollar store down the street - if it makes you happy, it doesn't matter the cost or rarity; not to a collector it doesn't. Speculation is nowhere near as enjoyable, since you could be speculating about anything - playing cards, comic books, commodities, stocks, property, rare metals, raw gems, doodads, whatchamacallits, thingamabobs, tchotchkes, whatever; it doesn't matter much to the speculator - if he or she can buy it now at one price and sell it later for more, that's all that counts. The collector enjoys what they're collecting, while the speculator enjoys what the collection might later bring - cash, that's it, nothing more.
