The deal that's really best
Basically, the "Best Deal" tab isn't the lowest price, but the "highest bidder", which isn't a huge problem when you have an ad block that's big enough to show all the prices... but with a one-price-listed block, it's kinda misleading.
UPDATE: Frye was nice enough to post and comment that I totally screwed this up, which is right -- I had it clear in my mind, but my words just didn't explain reality. And now that I've played with it more, it's clearer, too.
It's the "Best Deal phrase on the default Description tab" that isn't the lowest price. But the Best Deal tab actually does show the best deals, assuming you have a big enough ad box that you can see more than one price. The highest bidder still is at the top, but if the Chitika ad box is tall enough that it displays more than one price, you'll see if the second or third price is cheaper. Hope that makes sense! :)
So, until we get that hashed out, don't buy things from Ruth's blog thinking that you're getting the best price!