RAR is very low at the moment, and if they sell for below $150 you're getting a bargain. In terms of products for D&D, it's one of the best to have been published in the past decade. A gap no collector should have if they have the chance to fill it.
CSIO is incredibly under priced, now selling below cover price, less than half where it should be. These should be up at the $80-$100 but are down at $40-$50 at present.
Wilderlands has maintained it's value in the current downturn. It should be selling at around $120 and seems to be doing so quite consistently.
City of Brass remains a turkey shoot, it sells as low as $30 and as high as £80 with no real rhyme or reason. It should probably be priced somewhere in the middle. In reality it's not that great a product; the one most likely to disappoint the buyer.
Thracia is a sub-$10 module, probably costing more to ship and pay fees on than to sell.
IIRC I picked up a dozen copies at $3 each a few months back.
Larin Carr is in the $10-20 bracket. It doesn't come up as often as the other NG modules, and is sought after by the NG collectors for that reason.
Abysthor is an often overlooked gem. A little 8 level mega-dungeon in quite a hefty book. Think of it as Rappan Athuk's Little Brother. Sells on the whole between $30 and $50 depending on condition, and well woth that sort of money.
This week I've been mostly eating . . . radishes.
