NOw, now guys, this is becoming a rather nasty fight and very un-necessary.
I prefer baby potatoes, but that is just me. I actually dont eat much starch at all. A bag of potatoes lasts over 2 months in our house. Did not say I would/could not eat full size spuds, I just prefer other cultivares.
And believes or previous careers aside, this is a healthy discussion about yeilds and as John put it, Can a family feed themselves off small or no available land. Ultimately it is an experiment for self gratification and does it benefit you to grow your own produce. Costs aside I believe if you have an option/decission as to what goes into the mix in the form of chemicals, soil types, nutirents etc you know you are eating something healthier than the store bought possible genetic modified stuff. If you can buy from Woolies and take organic only produce etc then you aren't cared about the costs, and growing your own comes basically down to just do you want the effort of doing it?
If you are shopping for the basic "get as much as you can for your moneys worth" then every saving helps and here the idea of growing a yeild bigger/healthier than store bought options is a way to consider it with little input costs. most of your watering could be grey water from your bath/shower/ hand basin so in effect recycling water. (here inorgaig uptakes etc could be factored in but then again the carp in the air collected by rain that falls on a farmers lands in likely to be more toxic than your bath water). Soil is reasonably cheap/free to obtain and re-useable just adding the minimal required extra nutirent for spuds to grow.