The test for a classic is not sales, it is whether the argument still works now. Every book here was published recently enough to be about the current economy and has been out long enough for its claims to have been tested by events.
That second condition matters more than it sounds. A book praised on publication for identifying a trend is only a classic if the trend arrived. Several very famous titles fail this and are on the overrated list instead.
What these share is that they changed the vocabulary. You will hear their terms used by people who have never read them, which is the practical reason to read them properly — the shorthand usually loses the qualification the author was careful to include.