Okay, here's the deal. Sainsbury have a half price promotion on Maipo Sauvignon Blanc. It's down from £6.99 to £3.49 a bottle.
However, buy 6 bottles of (any) wine and you get 25% off.
BUT... the till takes £8.35 off box of 6 bottles, meaning that it's £12.59 for 6 bottles or £2.10p per bottle.
Review (showing it really was at the higher price!)http://www.alastairbathgate.com/2008/06/07/vina-maipo-sauvignon-blanc-2007/