People are anchored to prices, usually the first price they encounter for a specific item. This holds true even when the first price they encounter is negative meaning that something can be perceived as a punishment or a reward depending on how it was framed initially.
From Toby Segaran's notes on Dan Ariely's Predictably Irrational. Emphasis added.
I find it interesting how people deal with pricing of items in general. I heard an NPR story this morning about how researchers found that people perceived exact or precise pricing as being a better deal even know it wasn’t in the research study.
Some genius will be able to make sense of first and precise. Other than Wal-Mart that is.