Makes sense. Personally I'd like to move away from USB HDD storage and just have everything flash memory (less crap to carry when I travel, less noise, one less thing to plug into A/C) so I don't mind the extra expense for a half terabyte card. From my backed up collection I probably have about 300GB worth so I could definitely use it.
(Incidentally: wow. Half terabyte on a tiny little scrap of plastic. When I was a kid 512MB was a large storage size, a friend of mine bought a 3.5" Seagate IDE harddrive for his Amiga and we never filled it even 25% up. It cost more than £149, and that was in 90s prices...)