To update this: it seems that sometime before mid-2013, the cheaper generics finally started percolating out. The earliest mention I've found so far is from May 2013:
How odd, I pay a little under $60.00 a month for for 450XL Watson generic (never any difference for me between Watson and brand).
A Redditor today mentioned it:
If you don't mind, I'm trying to spread the word that COSTCO now has a generic that is only about $170-270 a month depending on dosage (about $800 cheaper than elsewhere). It's made by Watson labs. As far as I can tell only COSTCO sells it right now.
Due to agreements with the patent holder, Cephalon, that were made in 2005-2006 several generics manufacturers are now allowed to sell generic Modafinil. I have found confirmation that the manufacturer Teva has begun selling generic Modafinil, though I haven't seen news about other manufacturers. However, the article also, says that Cephalon is a subsidiary of Teva, so perhaps this won't have an effect? The Modafinil patent is set to expire in April 2015.