I think I would need over 1000 wheelsets just to do the cars I have now. That would only leave 19 other like minded Z Scale modelers in the world to suck up the rest.
I did purchase 10 packs of the Nn3 wheel sets, and they work great, but they are 36" in Z, so I use them on tenders only. Also, I paid about $80 for them from RLW, then later I spend several more dollars on the metal bushings so I can get electrical pickup capability.
I would really prefer the wheels to be made with an axle nub and point, as 1 piece metal, then slide it in a plastic tube, so all wheel electric pickup in a Kato style caboose truck or tender truck would be possible.
As far a bulk prices go, how do companies like Intermountain offer retail pricing of N wheelsets in a 12 pack that are found for under $8. That's less than $2.75 a car full MSRP. Surely they did not order much more than 20,000 pieces, because everyone and their cousin sells metal wheels in N.
N Scale Supply off's their Atlas 12 pack of metal wheels for $5.80, or less than $1.95 a car. With an MSRP of $7.25 a pack, which following the 3X rule to make any margin at all, means they got them for 20 cents each axle.
At that price I would be willing to invest $4K for 20,000 blackened Z wheels sized to fit MTL trucks, and break them into 12 packs to off through Walthers. If I threw an add in Ztrack, N Scale, NSR, and MR, I think that half of them would be sold in a few months. This would leave a lifetime supply to my head! (that's the real goal anyways) Even if these were the exact shape and size as MTL wheels, it would be better and more consistent than plastic wheels.
-Robert