I am a huge fan of breaking down how much something really costs. You buy a box of donuts for $5. If there are 12 donuts in that box, each donut costs you 42 cents. It's simple. I think a lot of us do this at the grocery store. I know that my grocery store lists the unit price on the shelf tag as well as the price for the item. This makes it very easy to figure out whether the 10 pack or the 20 pack is the better deal.
But I do this with things other than food. My gym membership costs me $60 a month. If I use it 20 times a month, it costs me $3 each workout. Not terrible, especially on the days when I take a class. But if I suddenly only use it 15 times a month, each workout costs me $4. Even though I pay the same amount either way, I feel like I'm getting a better deal if I force myself to use the gym as many times as possible each month.
The (free) running log I use allows you to enter in your running shoes and then track the mileage on those shoes. For those of you who aren't runners, this is important because unfortunately, shoes do have a mileage life, usually somewhere from 300-500 miles, though it can be less. You know that your shoes are starting to wear out when your joints start to hurt, but it's always good to have some sort of an idea of where you are in terms of shoe mileage. This site also lets you put in the purchase price and then tracks how much the shoes cost you per mile. It's fun to watch that number go down. Right now, I'm rotating two pairs of running shoes and they have cost me 57 cents per mile and 39 cents per mile and still have a number of miles left on them. Combine that with my average running pace, and well, those shoes have lasted a long time. Definitely worth the price.
Since signing up for Netflix, I have also signed up for FeedFlix (also free). You link this site to your Netflix account, tell it which plan you're on, and it tells you all sorts of stats about your Netflix account, including how long you typically keep movies, how much you pay per movie, and how that compares to other Netflix users. Sure, you could figure out your price per movie by yourself, but why do the math when there's a site out there to do it for you with just a few clicks. Since I've just started using Netflix, this is a good way for me to decide whether or not it's really worth the cost.
Sometimes, if you sit down and figure out just how much you're paying for something, you realize just how worthwhile it really is, and other times, you realize that you're spending way more than you thought and this great deal isn't such a great deal after all.