I find the Old school wisdom and straight talk approach he dishes out much to my liking and a refreshing variation on the hucksters appearing every few years always trying to sell you the latest snake oil.

Replace the sink with a double sink and explain to them the old fashion method of hand washing dishes .Tell them as is , plain and simple

I started out at the humble beginnings of being a dish washer and have worked my way up to the top as an Executive Chef. 

If you have a 5 BR, you're probably looking at at least 12 people, 6 beds, 12 sheet sets, 24+ towel sets, 12 dish sets, etc.  

I drive around and my mouth waters.

Another alternative is to use Dawn dish detergent.

Dish washer/ washing machine/ big appliances create heat and eat electricity even more if they are old. 

Does that price include linens, paper products, dish and dishwasher detergent, etc?

If you just use occupants as the deciding factor, they may come back and say that 2 people don't equate to 2x the usage of water because they do their dishes together, laundry together, and sometimes may shower together. 

Problem is the 3/4 in hardwood was installed way after the dish washer .