I was curious how much contact solution I go through in a year, so I wrote the date on the bottle when I started using it:
So since it lasted 7.5 weeks, that means I need to buy a bottle roughly 7 times a year. At $9.27 a bottle and 52 weeks in a year, that means I spent about $64.89 a year on solution. That's really not that much. But if I spend the same amount on the cleaner, I might want to see how much it would cost to get an updated prescription for my glasses.
This obviously isn't a solution to all of your financial problems. But it would be an easy way to figure out how much you spend a year on everything from cereal to toothpaste. If you are trying to decide if you want to make your own _________, this might be a useful exercise.