It means those of us who own jackets have willing buyers. It lowers the risk to entry a little bit. If you are not sure something will fit or work with your style, there are plenty of people who will very happily pick up a used TOJ. You'll have to sell it at a discount, but it seems like less of a discount than a similar non-TOJ garment might require.
Imagine trying to sell a MTM blazer that you ordered from some guy in japan who's got a company in korea who put it all together for you--no, they don't have a website, just an email and a tumblr with some pictures. I don't know much about the going rates of used TOJ, but it sounds like you can sell the core pieces at what...a $150 discount? Much more willing to take a risk if that is all that is on the line (you're going to lose a lot more money trying to sell a MTM/custom piece from somewhere that's not a forvm favorite)