The Z3 price drop in the USA may be attributed to the Rear Subframe failures being experienced here. I own a Z3 and a 1992 Miata and the Miata dances circles around my Z3 in performance, handling and durability.
My Z3 has a broken Differential bracket and Subframe breakage. It is happening to quite a bunch of us here, from weekend completely stock canyon cruisers to those who modiy their Z's. Tha's why I bought the Miata.
Have a Look if you wish:
Why not join a Miata club you ask? Miata has 185,000-miles on it and no loss of compression or excessive oil usage...i just may. I do a Autocross in parking lots maybe 6 times a year and the stock Miata's consistantly beat the stock Z3's fairly easily. The Z3 only beats Miata in looks but Miatas are almost indestructable and age incredibly well.
Thanks Gents and enjoy your Z's