From their initial release, there's only a thousand or so (if that) made with the Farm Technology Days (nee Farm Progress Days) stamp or sticker. The tractor &/or impliment is usually representitive, as of late, of a tractor that is or was used on the host farm for the show. A majority of the special tractors are sold at the show, while most of the extras go to the neighboring dealerships where that brand is sold, i.e. the 340 could be found at area CaseIH dealers, Oliver at the Agco dealers, etc. Tractors left over from the show, will end up with venders you find at toy tractor shows, internet stores & the rest go to the tractor dealerships.
The tractors without the show stamp are either held during or manufactured after the show. I would wager they try too sell as many as they can after the show to offset the tooling costs for the dies to produce the models.
With only a handful made for the show, they might fetch a few extra dollars. The price might rise, over time, once all of the show tractors are absorbed into everyone's collection & collecting dust. DON'T believe everything you see, in terms of price, on Ebay or other auction sites/houses. Unless the tractors sold out at the show & dealerships, they ain't worth $999.99 at a "Buy It Now". Keep an eye on regular, usually non-reserve, auction prices that start disgustinly low. If the tractor is in demand, the bidders will be the proof. Keep tabs on the prices for, say, a year. Then you can bid comfortably, "Buy It Now", or find it at a show or dealership at a better price. That's my opinion on prices, anyhow.