Yes these things always seem to go for vast amounts of money, far more than one would think they would be worth.
They are of course beautifully engineered, probably very effective and a far better ?solution? to providing 10 Inch reel capability than the Stellavox rubber band affair that they came up with. But for the combined cost of a Nagra portable and one of these adapters one could probably find a rather better full size recorder with large reel capability in the first place.
But there again if you are a Nagra collector with pots of cash, what?s the problem?