I think I know what they're doing

Since most people don't know/don't care about DRM, the only advantage in their eyes would be the higher quality for 30¢ extra. And since you can't really tell a difference between 128 and 256 AAC with just an iPod and the stock headphones, people won't see any advantage. In the end this will tank, so the RIAA and Apple can wave a finger and say "I told you so!"