Mind Hacks links to discussion of eBay auction silliness. In trials, people prefer to pay $5+$6 shiping for a CD than $10 for a CD with free shipping. It was a controlled trial:

multiple auctions with different price-postage ratios revealed a net preference for low item price and a poor correlation between auction success and stated postage costs

Now the obvious thought is that we’re sub-rational idiots. However, if I was presented with 5+6 or 10, I’d not buy the 10 because I’d be looking to satisfice 5+x<10. It’s one of my big gripes about online shopping that sites try to hide shipping charges. I’ve abandoned many shopping baskets due to unexpected shipping charges that weren’t at least mentioned at “add to basket” time.

Ortholog has a nice tie up with “Influence“, which looks like a good discussion of why we do the things we don’t want to.