The lack of 128's on the market in the past was because everyone was using their 128's, now that more and more people are moving onto 512, you'll find that 128s will become more and more common.
1.5k is dirt cheap, but who knows, they might drop as low as 1.2k per texture, due to availability, but i doubt it, once users current stock within the market drops, the price/value should become more stable.