A few readers have wondered whether online stores like Target are legally required to honor listed prices the way some brick-and-mortar stores are. In Target's case, no, they are not required to honor a pricing error online. That kind of error is covered in their Target.com policy statements, which says that they have the right to cancel an order and notify the purchaser of the cancellation if the correct price is higher than the stated price.
Drastic price reductions are fairly rare for the Britax Marathon, a car seat that is popular for its high harness weight limit, side-impact protection and ease of use. The unusually low price lead to posts on many online parenting and car seat forums alerting others to such a great deal. It didn't take long for would-be Marathon buyers to report that Target.com was sold out of the car seats in both incorrectly priced patterns. Though some buyers ordered several seats hoping to make a profit later, many were parents who otherwise considered the Marathon car seat out of their price range. Though the cancellation emails offered to let customers re-order the car seats at the regular price, these parents expressed regret that they couldn't afford to do so.
Update: Some of the customers who received shipping notices are now reporting that they have received their Marathon car seats from Target.com.