So I was able to find 1969 retail prices for most of the basic food items you’d use to make cookies here.  Someone more enterprising than I could probably figure out the utility cost of baking a dozen cookies using the other data provided. Although there were some gaps in the data, I came up with this:

Which, of course, means that the ingredient cost alone would exceed two cents per cookie on the plain sugar cookies, let alone the Peanut Butter and Chocolate Cookies we are also informed she counts among her wares.  So we have now thoroughly established that Mrs. O’Brien, while charming, was obviously not in it for the money.

We are lucky enough, because Rama is awesome, to have my copy of The Tiny Little House from when I was a small child.  Ian loves it.  We read it three or four times a day.  As a result, I’m probably overthinking this passage:

Alice took some paper and made a sign.

Cookies for sale very good ones

She put the sign in the window.  Then she spread the cookies out on the tablecloth.

Soon some people came.  First there were two boys with a wagon, and then a girl who was minding her little brother.

“Where are the cookies?” they asked.

“Right here, two cents each,” said Alice.  Then she turned to Mrs. O’Brien.  “Is that right?”

And of course, dear Mrs. O’Brien tells the sweet little girl that two cents will be just fine.

But, by my calculations, assuming her supplies cost her nothing and she did not pay for the utilites to bake these cookies (HAH!), Mrs. O’Brien would have had to sell 963 cookies a day to make the median income for a single woman over 65 in 1969, which was $7,025/year.

Also, she was baking these in a home oven. Even if you assume she could bake two sheets at once (doubtful), at the average cookie baking time of 10 minutes per sheet, this would be 6.666 hours of baking time, leaving her approximately 9.33 waking hours daily in which to sell 80 dozen cookies, all without the power of the internet.

I hope she had another source of income.  Also, I wonder what kind of mother is busy thinking about these things while reading to her angelic child.