I think 512's the biggest card they have atm, but those are easily hundreds of bucks (maybe $200 or more).
The deal in June worked like this: hope we get one soon again
Staples has it for $90, PM to Amazon's after rebate price of $51 (the rebate $20 said valid at participating vendors only). That made it just under $50. Toss in a few buck filler, get the free shipping, and use coupon code for 10 off 50. After receiving product, fill in $20 rebate anyway (people called and verified Staples to be a "participating vendor."
Too bad the above deal was long expired, and too bad Staples and Amazon were always out of stock. But basically, that's what it took to get a big SD for cheap.