It is too difficult to answer the question precisely because of the variables involved. However, there is one major factor which makes dry cat food cheaper than wet. This fact overrides any other in my opinion. And it’s this: you never waste any dry cat food pellets but you invariably waste some wet food because it is left in the bowl. And if it stays there for several hours under normal ambient conditions a cat might reject it permanently. It becomes fox food or waste.
Discarded cat food
Dry cat food can be left in the bowl pretty well indefinitely, in practice. I know dry cat food goes off but it doesn’t go off fast enough to the point where it goes off in the bowl. This is because it is eaten before it can go off and has to be thrown away. I have never thrown away dry cat food but I have, over the years, thrown away, I would estimate, about a quarter of the wet cat food put before my cat.
In other words, 25% of the wet cat food that I buy for my cat is thrown away because it had been left in the bowl and gone off. This must have an impact on any calculation trying to work out whether dry cat food is cheaper than wet.
Another variable is the quality of the food involved. Some wet cat food is very expensive and some is at the very bottom end of quality and therefore cheap.
Comparing prices – random selection
I purchase Hills Oral teeth care dry cat food, which is large pellets. A 7 kg bag lasts for 108 days which works out at about 44p per day. I’m working in British currency. In US currency this is $0.61. So that’s a per day cost which seems very reasonable to me especially as the food is high quality within the context of being dry cat food.
Comparing the price of good quality wet and dry on a per kilogram basis produces a similar figure. For example, Sheba Fresh Choice Fish Select Cuts in Gravy 6X50g costs £5.50 per kg while Hills 7kg bag of dry Oral Care (the product I referred to above) is £6.90 approx per kg. The dry is more expensive but Hills products are expensive. There are cheaper dry foods.
I would like to hear the views of others but in my estimation, I would argue that a good quality dry cat food is somewhere near three-quarters the price of a good or high-quality wet cat food on a per meal or per day basis when taking into account waste (uneaten food discarded). That does not mean that cat owners should feed their cat dry cat food only because there are other considerations that cost. Feline health is at least as important.
The general feeling among the experts is that the highest quality wet cat food should be fed to a domestic cat within the budgetary requirements of their owner together with some dry cat food of an equally high quality for perhaps night-time grazing.
I prefer oral care dry cat food because the pellets are much larger which prevents cats swallowing the pellets without chewing on them and also it can arguably help to clean the teeth. I think all dry cat food should be as large as oral care dry cat food.