Who wrote this?

[subnumine]

• Prices, whenever there was no monopoly, came earlier under the influence of competition, and are much more universally subject to it, than rents: but that influence is by no means, even in the present state of intense competition, so absolute as is sometimes assumed. There is no proposition which meets us in the field of political economy oftener than this-that there cannot be two prices in the same market. Such, undoubtedly, is the natural effect of unimpeded competition; yet every one knows that there are, very often, two prices in the same market. Not only are there in every large town, and in almost every trade, cheap shops and dear shops, but the same shop often sells the same article at different prices to different customers; and, as a general rule, each retailer adapts his scale of prices to the class of customers whom he expects.

John Stuart Mill.

This has changed since 1848 only in that the merchant has posted prices, and does not usually charge a different price to Lady Bountiful and to the shop-girl from down the street; but coupons have much the same effect.

For years, you could get the local cider in half-gallons at two stores across the street from each other; their prices differed by $2, and continued to do so. The situation has changed only because one company sold their store to new management, who ran it into the ground by not paying their suppliers; but it was stable before that (and the one that went out of business had the lower price).

For another example, the library in which I type this sells two types of flash drives: ($10, capacity 2 Gb) and ($13, capacity 2 Gb, with a pretty logo of the Office of Information Technology in the school colors). I inquired, and found

• This is not product differerentiation. They have sold one of the $13 flashdrives, and that was a time when they were out of the $10 ones.
• OIT used to supply flashdrives, with their logo, all over campus for $13; when the Crunch came, two years ago, they told the library to get their own. The library found they could get plain flash drives cheaper; the $13 stock is what they have had for two years.
• The student body appears to buy OIT. Presumably they don't know the library has the cheaper version.

In short, market forces work, when there is a market; but often there isn't one. Having a market requires transparency; which may explain why our loudest worshippers are generally opposed to transparency.