I'm not actually a fan of the idea of the absolute cheapest price. It's often far more expensive in the long run, and we should take the long view if we really want to save money.
One of my favorite examples is modern mass-produced clothes, usually imported from countries where the work is shoddy and the materials even worse. Clothes that can't be worn (i.e. socks that won't stay up) or fall apart or come apart at the seams within two or three months of light wear are essentially disposable. In fact, the quality of most of the clothes being imported is now so bad that I think that paying someone to tailor at least some clothes for you (skirts and possibly pants and jackets) is probably a viable money-saving strategy. Of course, learning to sew yourself is better, but I admit to being sewing-impaired, and unfortunately I don't know anyone local to me capable of tailoring clothes for me.
Another place where I opt for quality over cheapness is my peanut butter. I buy the natural PB that has to be refrigerated, and admittedly, I could save money with regular PB. But the natural PB doesn't have partially hydrogenated oils or added salt, plus there is almost no comparison in taste to me, and I think those things are important enough to spend the extra. I do watch for sales and stock up then, and recently I've been able to get one pound jars for $1.25 each. That's less than $.10 for an 8 gram serving of protein, which is still a good deal. And this is my "emergency" food: when I don't have much time in the morning, I make PB toast for breakfast, helps me resist the temptation to buy fast food.
I've mentioned our reasons for drinking organic milk before. I also use an organic toothpaste. Yes, it's more expensive. But one tube lasts quite a while, which means the actual difference in expense per month is pretty small, and it's produced in the US. Most important, I trust this brand, and that matters. A lot. I'm very leary of food and oral products produced in countries with much lower standards of quality.
Which brings me to food safety (and any other kind for that matter). Saving a few cents is NOT worth risking food poisoning or anything else. If we have meat that goes past what I feel is a "safe" age limit, based on safety recommendations, it goes into the garbage. $5 for a roast, or a $100 copay for an emergency room visit, plus possible treatment, missing work and classes. It's just not worth it.
Just last Saturday, I made my lunch for the next week, fixed myself a bowl, then put the rest in a container. It was still pretty warm, so I left it on the counter to cool before putting it in the refrigerator while I read for a few minutes. Two hours later, I woke up from a nap. Ooops. I did eat the one bowl out of it, and I comfort myself a little with the knowledge that this particular one was an experiment that was barely edible. But while I hate wasting food, I'd feel a lot more guilty about ending up in the hospital to save about $.60...