So, sometimes we look at price and say "Holy Crow! $x for that??"
Most of us here look at unit price, take a deep breath, and say "ok, $x per y units, and that is better than what the other place charges." That's the Costco logic.
I propose that some unit pricing is better done in terms of time: $x per day or week or month. Here is a (semi-true, but numbers made up) example:
Our friends used to buy enormous discount bags of chocolate chip cookies from a military commissary. Per ounce, they were a steal, but the bags were enormous -- for the sake of argument, say 2 pounds, 200 cookies, and 12,000 calories, with a lot of artificial crap in them. Let's also say the bag was $5 -- a good deal in unit price. And, they'd eat them in a week.
At the same time, we'd buy a little gourmet 10-pack of cookies, 800 calories, all natural, also $5. And it would last us a week.
One week later, we'd both had cookies and spent $5. In my opinion, our choice was better -- in terms of health and hedonic adaptation. Our weight-unit-price was worse, but our time-unit-price was the same.
The time-unit concept helps clarify decision-making: whether to buy cheap shoes ($10/pair, but $30/year) or expensive durable ones ($60/pair but $20/year), for example. It's really good for balancing gas price against your driving habits (will this $40 tank get me through a week or a month?) Some things it won't help -- onions are onions are onions -- but it might be useful addition to your budget thinking.