How much tinned cat food per cat per day?

Ive recently changed my cats over to wet food, but they are eating me out of house and home. They are quite capable of eating a tin of Whiskas (14oz/200g) EACH per day. A friend mentioned this morning that her cat gets half that, and I was originally giving them 1 tin between them per day. So are they leading me up the garden path when they tell me they are hungry?