I found an exact flash replacement for my MMI M112 drive:

http://www.datexdsm.com/disc/disque33.html

But the price is not shown, which leads me to believe it may be as costly as you suggest, Gorgonops! I'm afraid to even ask them about the price!

UPDATE: I just found out the price. Sheesh:

http://datex-boutique.com/product.php?id_product=47