I know that Mega has a reputation for being an expensive supermarket. And I do find that for some things they really are, but for other things, they are decently priced (remember they have been advertising that they are selling certain price regulated items at a discount of 10%, making 1 liter of 3% milk cost 4.50 NIS).
Well, I just discovered that certain Mega stores are now offering a storewide discount of 10% (although certain restrictions apply) if you shop on Mostaei Shabbat (with a "You" card membership - which is free. Just take a minute to sign up at the store!)!
My local store is not on the list, but there are plenty on the list that may make it worthwhile to shop on Motsa"sh!