I think its a little naive of the community to think that these "new" miners are shipped right off the assembly line.  I would think they've been running them for weeks or possibly months and then offer them for sale as new when there is a modest gain above ROI for the buyer.  I find it funny how new BM miner ship dates just happen to coincide with a diff increase.  Probably not just BM either...it's just a matter of corporate greed in a relatively new market.