I could be wrong but I seem to remember somewhere about the early being 6 ply rather than 8 ply. I should do some research but if I am correct the first year it was 6 ply and may be worth more to some speculators.
I was not aware they changed ply count. I thought they were always 6-ply. Interesting. That said, whatever those kits retailed for will still determine its current value, I think. It's not a collector's market, so I doubt people are counting plies. It's a good thing and a bad thing. The market for used entry-level kits is stable for both buyer and seller. The bad thing is no one can really make a buck on new entry-level kits so many retailers consider them a loss-leader to compete on the back end. Sort of like convenience stores taking a loss on gas to sell you a $5 energy drink.