The comment about discounts was because 5% is a lot when it comes to groceries (typical profit margins are around 1%)
I can think of several reasons why typical markup rates would be relevant, but not for why typical profit margins would be. I suspect you looked up "profit" when what was doing the work in your implicit arguments was "markup". 5% then ceases to be thought of as 500% of 1% and becomes thought of as a more reasonable 33% of ~15% or so.
charging people just 5 cents per plastic bag causes plastic bag usage rates to drop significantly.
This is because humans are irrational about free things, rather than the sum of money involved. See Arieli's Lindt/Hersheys experiment. It is possible they see checking out as free, but also possible they see the price as a surcharge on each item. I don't know.
Also, I think your emphasis on what you see wrong with a 5% toll violates the spirit of least convenient possible world, as I used that as an example of what I thought would approximately achieve the ends I had in mind.
perhaps 5-10% of customers are time-starved enough to pay extra.
Rather than create something entirely new, with different advantages and disadvantages (e.g. someone has to be there to take in the groceries, but one doesn't have to go to the store), I am discussing a small improvement to an existing structure. I don't really buy the analogy because the point of this is that people could decide what to do after going to the store that has choices and looking at the lines. People like to keep their options open. They don't have to decide yet how impatient, hungry, or busy they are.
There's also the question of the time calculation from the customer's point of view. Suppose they save 5 minutes; at $8 an hour that comes out to 67 cents. If the order costs more than $30, that's not worthwhile.
Here you predict people will be rational, while I predict they will be impatient for an immediate reward. I also think orders of less than $30 and people who make more than $8/hour are pretty common.
I can't remember the last time I had to wait more than 2 minutes to check out.
To this I'm going to invoke LCPW again. From 5pm to 7pm where I live, lines are long. The toll lane doesn't have to be active at 10am.
I can think of several reasons why typical markup rates would be relevant, but not for why typical profit margins would be. I suspect you looked up "profit" when what was doing the work in your implicit arguments was "markup".
Profit margins strike me as a better measure of how competitive prices are; markup rates are necessarily higher because of the costs of running the store. To put it another way, high profit margins are a better sign of low competition than high markups.
The argument I was making was that grocery store customers a...
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