How much per snake do you spend setting its enclosure up? If you have a single expensive item (such as a thermostat or rack system) running multiple snakes, divide the cost of the item among the number of enclosures it regulates.
I realize the numbers will be all over the board, but I'd like to get a feel for what people spend to acquire a snake outside of the cost of the animal itself.
Formula:
Total $ invested in husbandry supplies (thermostat, thermometer, tubs & racks, etc) / # of snakes you have = cost of housing per snake.