now ppl sell SD from 256MB onwards. unless you have an ancient
device that does not support, you could take my 64MB SD for a token
fee. and to think of it, i got it 4 yrs ago. 
also, do check carefully if they mentioned only SD (Secure
Digital), or MMC, RS-MMC, DV-RS-MMC, MMCMobile/MMC Plus,
microSD/TransFlash or miniSD.
256MB SD Card can be gotten from as low as $22. RS-MMC from $30.
DV-RS-MMC from $38. miniSD from $28.