As for monetary value, I'd also be interested to know. My sense is that, though rare, they're still undervalued due to the post-buyout chill. Regardless, there are lots of testimonials on the Forum to the virtues of late 400s.
I have refurbed a couple of post THC 400 Altos with the back bell keys in and around this serial period ...and honestly, they were shockingly GOOD.
I mean I expected the keywork to be clunkier and less responsive and the blowing response to have been negatively effected....sort of the difference between an earlier 'Crat and the S-33's is what I had in my mind.
Indeed they were NOT THC body specs (although interestingly thanks to some data provided by Maddenma, neither were they straight-up Aristocrat body specs as you sometimes hear they are).
They were actually great playing horns.
If memory serves the Altos could fetch only around $650-700 however, completely overhauled.
The Tenors of this period, in playing shape, I have never seen sell for more than $1g and I think in most instances that would require some patience on seller's part to get. Project ones I have seen tended to stay under $500.
If the Tenor is as good as the Altos are, then they are serious sleepers as well.