There are many app sale tracking services and sites, but I've never noticed one that shows sales on IAP's. Do IAP's go on sale? Are there sites that track these sales?
They do go on sale sometimes, but it obviously depends on the seller. Namco's addons for Pac-Man Championship went free recently, for example. I don't know of any site that tracks these, however. At least they're cheap though.
I suppose sites like App Shopper don't track IAP sales because they can't get a referral commission out of it, huh?