Rainy Day Creamy Potato Soup

Last night we deviated a bit from our weekly Menu Plan. It was cold and rainy yesterday, and since I had all of the ingredients on hand I went ahead and made one of my favorite rainy day meals. I love to serve it with some buttered french bread. Creamy Potato Soup. I first had this soup when my old neighbor shared it with me. I had to get the recipe. Since then, I have made a few tweaks to it, and adapted it for our family. 
This soup is very hardy. It will fill you up, and keep you full. And, It. Is. Cheap. Seriously, it's got to be one of the cheapest meals in my rotation. The Cost Per Serving= CHEAP! (I was going to try for the cost breakdown, but that was a lot of work, so I gave up. The best I could come up with was about $.43 per serving. And that's probably a high estimate, because there is leftovers.)
I'd like to share the recipe:

Peel & Cube 6 Potatoes. Save 1 Cup of the water you boiled them in. Set potatoes & water aside.
Saute 3TBS Butter & Chopped Onion (I usually use only 1/2 onion). Slowly add 3TBS Flour to the onion/butter mix.
In large pot, combine the potatoes, and the butter/onion/flour mix.
Add the 1 cup of potato water that you reserved.
Add 3 cups milk.
Add 1/2TSP Sugar
Add 1 cups of shredded cheese.
If desired add chopped ham or crumbled bacon.
Simmer on low heat for 30 minutes, stirring often.

Garnish with sour cream, shredded cheese, bacon bits and/or chives if desired.
ENJOY!