The base price is the highest price I will pay for something. Being a quintessential cheapskate is more a mindset than anything. I have a mindset where, for example, I won't pay more than a dollar-fifty for butter. Of coarse I won't let my family starve because prices are too high. The trick is to know when the next sale is coming, to anticipate. After following your local grocery store's sale cycle for a while, you should get a good idea of how long they go between putting certain items on sale. Every 5 to 6 weeks, for example, my local grocery store puts milk on sale. The best price I could find for milk used to be $2.50. This was my base price. Recently, my local Aldis has had milk at $1.89. This is the lowest price I can find locally, so now $1.89 is my base price. Of coarse since Aldis priced their milk at $1.89, the other local grocery stores have followed suit in order to stay competitive. Their milk price is usually higher, but their sale price is typically now $1.89.
The point of all this is to keep track of what local prices are for specific items you usually buy. Keep track of when these items go on sale at your local grocery stores. Be sure you keep track of at least two different local grocery stores in order to consistently find the best price. This may take some practice at first, but after even a few months, it becomes second nature.