Found this today, and it looks like a clearance sale. The big carry packs (58 of size 4, 50 of size 5 or 40 something of size 6, not the smaller normal carry packs) are being sold of for 5 pounds each - regular price is 9 pounds. At around 10p a nappy it is a very good price for this size.
This seems to be of the ongoing changes in the nappies section, so it may be store specific and/or until stocks are gone. This was in Leicester.