"Food" is cheaper here than UK. I put it in quotes for the following reason:
If you try to eat same/similar - then yes, you will pay a lot more for imported as well as relatively expensive ingredients.
However, if you compare a typical local family food budget to a typical UK/EU/Aus family food budget, you will find local is a lot cheaper. Locals eat a lot less meat, a lot more rice and a ton more veg.
If you want cheap - eat like locals (or Asians in general) do.