My neighbour's cat (who thinks he lives with me) usually eats about one 400g of cat food per day in my house, plus what he eats in his 'proper' home, plus what he almost certainly gets in other houses in the street, plus the stuff he begs from my plate, plus the cat treats I give him, plus various bits of the birds which he insists upon dismembering underneath my desk.
I used to have a VERY large cat (who actively sought out and chased big dogs!), who got through a minimum of 600g of cat food per day.
Chris