What is a good price?

I have had several questions asking how do I decide if an item is a good deal.
For quite a while I kept a notebook and jotted down the current price of an item, including the size and store I found it at. I noticed I needed to break it down to price per unit, oz, pound, diaper, etc. After a month or two I noticed quite a difference in the prices even at the same stores. So here is my current list to some items to get you started. If an item is more than my price point I will only buy it if absolutely necessary. If it is below my price point I stock up.

Cake mix box $0.50
Cereal box $1.00
Cheese per pound $3.00
Chicken (breast) per pound $2.00
Chicken (roasted) whole $5.00
Chicken (whole) per pound $0.79
Cleaning supplies bottle $0.50
Deoderant stick $0.50
Diapers individual $0.22
Dog food pound $0.50
Emery boards package $0.25
Fish 8 - 24 oz. $2.00
Frosting tub $0.50
Frozen veggies box $0.50
Frozen veggies bag $0.50
Fruit, fresh pound $1.00
Fruit, frozen pound $2.00
Granola bars per bar $0.15
Ground turkey pound $1.50
Hot Cocoa 10 pkts $0.50
Juice bottle $2.00
Lipstick stick $1.00
Liquid soap bottle $0.40
Mascara tube $1.00
Nail clippers $0.25
Nail polish $0.50
Nuts per pound $3 - $4
Paper towels roll $0.75
Pasta package $0.50
Peanut butter jar $1.00
Potatoe (dried) box $0.40
Rice pound $0.50
Snacks for lunch individual $0.25
Soda can $0.25
Soda 2 litter $1.00
Spegetti sauce jar $1.00
Toilet paper dbl. roll $0.50
Toothpaste tube $0.50
Tuna can $0.50
Turkey (whole) per pound $0.79
Yogurt, Jell-O indv. cups $0.25