Hands down Dairy (cow or goat) milk is the cheapest to produce...

Hands down Dairy (cow or goat) milk is the cheapest to produce and has the least burdon on the environment even more so in times of average rainfall because it further reduces the need for additional irrigation for fodder.

Nuts and other alternatives to milk all require year round irrigation which basically isnt affected as significantly by rainfall as growing fodder they still require a considerable amount of additional water.

Basically vegans and the like are doing more damage to the environment than traditional farming ever has. but while the demand is there im happy to invest.