A quick search on Amazon shows the most affordable 128gb SDXC card to be only $74 with Prime shipping:
www.amazon.com/Komputerbay-Secure-Digital-Extended-Capacity/dp/B003SGCO3E/ref=sr_1_26?s=pc&ie=UTF8&qid=1371160828&sr=1-26&keywords=128+gb+sd+card
I'd rather pay that to store my iTunes library, photos, videos, and books than Apple's $200 upgrade.