I noticed two days ago that Apple had the standard 12" iBook available for $799 as a refurb. Now today it's up there for $849. Is this standard practice that they fluctuate like that? Does Apple just sort of decide what to list it for depending on how many they have a particular day or was the lower price just a one day mistake? Also, is there a best day of the week to look for the refurbs? Thanks.