You could say the same thing about the microprocessor company they bought, why not just buy Atom chips from Intel or ARM's chips?
Owning the IP/patents for high density 3-bit and 4-bit NAND flash would give Apple a definite pricing advantage over their competitors who would than have to pay royalties to them (hmmm, wonder what Steve Jobs would charge them). And yes, I do believe Sandisk will be revealing their 3D R/W memory this year.
They would have to spend at least $10b to buy SNDK at this point.....they will not spend that much in nand....especially since most of the industry predicts the next new technology (memory medium) will happen in about 3 yrs.
SR1 is right about 3D.....if SNDK found a way to 3DRW, AAPL may be interested in that....but why? Are they not doing fine just buying it?