pricing and buying an nsx has not changed very much since i began following them some 5 years ago.
your NA1 coupes (91-94) will will be priced between 20k and 30k, depending on mileage, condition, accident history, service records, etc.
your NA1 'targa' tops (95-96) will be priced with around a 5k premium above the NA1 coupes.
your NA2 'targa' tops (97-2001) will be priced between 35k and 45k, depending on mileage, condition, accident history, service records, etc.
your NA2 'targa' tops (2002-2005) will be priced between 50k and above, depending on the same conditions.
prices for automatic nsxs any year have been around 3-5k less than their manual counterparts.
prices for the rare cars such as NA2 coupes, 99 Zanardis, etc still fetch very high prices, roughly 5-10k premium over their counterparts. With so few examples, the sellers really can charge whatever they want, and there will almost always be people willing to spend that extra amount to get these rare items.
with the economy the way it is now, prices have begun to slide slightly by at most 2-3k.
for 15K, you will be getting a very high mileage nsx with little to no service history, most likely deferred maintenance, salvage/accident history (whether it is reported in the title or not), and generally needing roughly the price difference between it and a good condition vehicle to bring it back up to par. At that time, the money you put into the car will bring it up to higher standards, but will not really bring up the value of the car.
if your friend got a no-stories, properly maintained, relatively decent miles nsx for 13.5k, then he got a real steal of a deal, since a car like that should go for 10k more.
i think pricing is very much along the lines of the S2000, except twice as much.
cost for AP1s = 1/2 NA1s
cost for AP2s = 1/2 NA2s (pre 2002)
i would say that generally, price for maintenance (larger items) and mods are roughly twice expensive for the NSX as the S2000. (generally)
