We have no particular allegiance to suppliers. The best price is all with regard to industry standard equipment and software, and we would recommend shopping around for both. As a charity we have aggressively pursued the best deal. To the point of sponsorship in certain cases. Experience has shown us that it is easier to negotiate on the price, or improve specification, of hardware.
Prices do fall, the computer industry is extremely aggressive.
But, though there has been some upward movement of late in memory costs, this is the 'how long is a piece of string' scenario. You would never buy on this basis. Finally the cost of installation and presentation within the museum has to be considered. It is insufficient to merely put a computer in a museum, it has to have a context within physical space in addition to being able to survive the rigorous use.