and this is the last on this (off the) topic:
http://www.rolandus.com/products/productdetails.aspx?ObjectId=657&ParentId=83#
(go to the "specs" tab, just bellow the image, wave memory)

and compare to this: http://www.rolandus.com/products/productdetails.aspx?ObjectId=968&ParentId=83
(the same)

i think we all agree GW8 does not have 8 times larger wave memory than GW7. the sounds i am sure are not 8 times better.
MB vs. Mb isn't really the issue, but maybe their marketing thought they can impress by high values.