You're right that cost isn't the only factor.
The cost of just the ingredients is not the biggest factor. Mixing your own clay is another time intensive step to add onto all the other steps of making pottery.
Can you afford the time involved? How about the price of the pugger? Compare the price of the equipment to make all the clay to how much already made clay actually costs...
I don't really want to put in the extra effort, but I probably have more time than money these days.
I have access to a mixer so I wouldn't have to buy any equipment, but I'd have to do some wedging.