The goal of any (for profit) enterprise is to make money. This is written into law in the United States (it’s called “fiduciary duty”, and it exists to protect the shareholders.) Under the traditional scheme of things, the normal process is that you build a better mousetrap (or lots of really cheap mousetraps), then you sell it at a price that will make you the most money: a single $1000 mousetrap and a thousand $1 mousetraps will have the same impact on your bottom line, so you need to find the happy medium that will make the most money.
The software industry has adopted a different model, however, one that other entertainment and digital content industries are trying hard to emulate. In 1908, the Supreme Court recognized the so-called First-sale doctrine, which was later codified in copyright law in 1976. In essence, the doctrine allows someone who has purchased a copyrighted work to sell that particular copy of the copyrighted work without the copyright holder’s permission and without the copyright holder gaining any further compensation. This is why publishers are unable to halt the legal trade of used books, movies, music and some software (especially games, console games in particular.) The software industry managed to do a partial end-run around the first-sale doctrine by changing the verbiage from one of a “sale” to one of a “license”. Even there, however, they couldn’t completely subvert the 1976 law, they could only make it more cumbersome.