> I tried this as an experiment to see if I wanted to order more music this way, but it only downloaded half the songs. Still a deal at 99cents, but not an experiment I’ll want to repeat with a full-price album.

This is "expanding the userbase", and seems overwhelmingly successful.

I've been thinking recently that "sales" (as in specials, temporary price reductions) are a socially acceptable way to do discriminatory pricing (different prices for different people).

You want to do this because some people are happy to pay more (so you want to charge the higher price), and some people will only buy at a lower price. If you price it high, you lose the low people; if you price it low, you can't charge the high people a high price. It makes sense to therefore have offer high prices to high people, and low prices to low people. But people hate this! Amazon actually tried it for a while, until it was noticed (maybe they still do, but in a less discernible way?)

A sale is a way to capture those low people, and only losing some high people. This is apart from getting them to be regular users.