Well that's not completely correct : only some of the Vocaloid are made by Crypton. They're also the ones that appear in the Project Diva games etc, so basically : Miku, Rin, Len, Luka, MEIKO and KAITO.
As Vocaloid is a software, there are many other Vocaloid (like vflower for example) which aren't from Crypton. 🙂