Yes I agree its a rip off for near 20 year old technology. I dont really care for anyones argument but Amiga hardware is far too over-valued.
With regards to Amibay, make sure you read their forum rules, in short dont talk about prices as its considered price driving. Not a rule I entirely agree with but its a great place and Ive been on there far more than here just lately (its also an Amiga.org type forum). If I was you I would have a browse of the listings and then place a wanted ad for the RAM card if you dont see what you like. Oh, and dont forget to put your location on your profile!