Tesco has been left back-tracking after customers used a price promise to cash in — some effectively ending up with free food and money to spare. The supermarket promised to give its 20 million customers a voucher worth double the difference between its price and Asda's in the "unlikely event" that products were cheaper when bought from their rival. However, customers have been taking full advantage of the deal, with several getting hold of vouchers worth more than £100 after searching for the items with the biggest price gap solely to claim twice the money back.
ASDA have a similar (but much more complicated) scheme, whereby if you don't save 10% over several supermarkets for "comparable items", they will make it a 10% gap. Typical savings of about £1 - £4 on a £70 bill.