hmm, that's a bit double though. BIO / diamonds and some lower skill books sell for enough to make it relatively easy for lower levels to generate a few million (for ores, the ones dropped from zombies 1st/2nd floor you can trade on the AH).
The most subtle solution would be the "everything someone sells in shops gets added to that shops inventory" system. Wouldn't immediately solve the GES issue (that's just raw market power), but the more general one of easy access to lower level items should be fixed.
Then there's the gameplay considerations... Giving lower level players some items / skills they can hunt for, but which will give them some satisfaction when they actually find them, is worth something no?