Once again, the mind boggles!  On a recent trip to the grocery store, I noticed plastic clam shells full of diced onions -- cost $4.99 for 283 grams (just over 1/2 pound).  I could get yellow onions, red onions, or a mix of diced onions and celery, each for that price.  I checked the cost of whole onions.  A three pound (1.36 kg) bag of yellow onions sells for $2.49 and a one pound (454 grams) bag of red onions sells for $1.69.

For the amount of effort that it takes to dice an onion, this seems like quite an extravagance, especially now, when people are watching their budgets ever more carefully.  Back home, I timed myself and it took 1 minute 40 seconds to dice a 230 gram medium yellow onion.  The result was 182 grams of diced onion ready for cooking.  The yield was about 182/230 or about 80% of the original weight.

Worked out on a per gram basis, then, the cost of onions is:

The last column shows the saving in cents per gram of dicing your own onions.  It may not look like much, but when you consider the cost of that 182 gram yellow onion times 1.53 cents per gram, it comes out to $2.78.  Pre-diced onions work out to nearly eight times the cost for the yellow onions or nearly 4 times the cost for the red onions.

So, where did I get the $100 from?

If it takes me 1 minute and 40 seconds to dice one yellow onion, yielding 182 grams, working non-stop I should be able to dice 36 onions per hour (3600 seconds per hour / 100 seconds per onion).

36 onions per hour X 182 grams per onion X 1.53 cents per gram = $100.25 per hour

Let me put this another way.  If every second day for a year you were to cook a dish that used one medium onion, you could waste $501 buying pre-diced onions.  It's almost enough to make you cry!