TSA is doing a PreCheck lottery for random people. I think of it as a marketing campaign to get people to sign up for PreCheck and pay them Money.
Paying $85 for PreCheck does not get you GE. GE does get you enrolled in the PreCheck Program and is very much so worth it if you travel domestically and internationally.
Nexus gets you Nexus and GE And enrolled in PreCheck as you are a US citizen (or so I am assuming).