I think that is the price for early adaptation. The record company is afraid of using a new media for distributing their music and hence they've upped the ante.
In reality, this should be a cheaper alternative to CDs on the cost of shipping side. You can get around 20 SD/MMC cards on the area of a CD case alone, volume-wise you can probably squeeze 4-5 cards (SD's are thicker than MMC) on the height of one CD case. Hence, for the volume occupied by one CD case we can get 20*5 = 100 MMC cards shipped! 8O That is a hackofa good music/volume ratio.
The problem is the cost of manufacturing a MMC/SD card thanks to the amount of metals (silicon, gold, silver... and such) that is needed internally in them. CDs compose mostly of plastic with a small amount of steel and aluminum (if mind serves me right) which is much cheaper to aquire.
I believe that those are the cost related causes for the higher Music MMC cards...
