There has been an uptick in the market, especially with the 1991 models as you can see from the graph below. Despite that, the "average" price is still below $30k. Of course there is always a disconnect between what the buyer feels is above average and what the seller feels is above average. The reality of course is that most cars are "Condition 3" cars and as such should be priced at $30k or a hair over, but of course most sellers believe their cars to be "Condition 2" or even the oddball who believes he has his hands on a "Condition 1" (highly unlikely) which explains the $40-50k asking prices.
On the flip side, EVERYONE (including dealers/collectors) are on the lookout for those Condition 1/2 cars as the car market is hot at the moment, so you will be competing with a lot of buyers. Despite the cold weather, the car market is doing well - probably because dealers are trying to get a jump on the spring market.
As for market correction, that is a real possibility as there are economic storm clouds brewing on the horizon for this spring. Quite honestly though, the uptick hasn't really been that sharp (check out Testarossa or 328 prices if you want to see a sharp increase that may crash) and I doubt that the NSX will suffer much of a decline in the upcoming 5 years. Most likely the cars will enjoy the steady slow appreciation rate that has been occurring since 2010.
With regards to the OP's question, it should be in a $30-40k range depending on how close it is to Condition 2 vs Condition 3. My guess is closer to $30 rather than $40 based on your quick numbers. I would not expect to be able to buy that car under $30k unless you are getting a good deal or there is a lot of information that we don't have about the car.