You can also make homemade dishwasher detergent. More recipes here
Comparing prices of dishwasher detergent isn't easy as the container of liquid dishwasher detergent shows weight (ounces) and not fluid ounces. The density of the fluid might vary and therefore comparing price by size might not be accurate. My dishwasher detergent cup takes 2 tablespoons of liquid to fill which weighs 1 ounce and so a 75 ounce container would yield 75 washes.
Whereas the pods have around 48 per container.
I haven't tried these recipes yet, but here are a few blogs that have recipes for homemade pods
One Good Thing
Family Sponge
Apartment Therapy