Thank you all. It was a beautiful model indeed, and seemed new. Looked like a lot of dubloons went into all that Swiss pear... Artesania Latina is located just outside Seville; I wonder whether they were involved at all?
And Allan, if I read the exhibit signage aright (my Spanish is woefully inadequate) then the Señora was also carrying guns as cargo, which might explain at least part of the discrepancy; and the Wikipedia article contains the following:
The Atocha alone carried cargo whose estimates range between $250 and $500 million, including silver from Bolivia, Peru and Mexico, gold and emeralds from Colombia, and pearls from Venezuela, as well as more common goods including worked silverware, tobacco, and bronze cannons.
Be interesting to know how accurate the model really is, do they have one at the Fisher museum I wonder?
Dave