The Rice University Neologisms Database

A "30k millionaire" is an individual who gives off the appearance of living a lavish and expensive lifestyle, but in reality, survives off a very limited income (i.e. only $30,000 a year). Negative in connotation, a '30k millionaire' is someone who concerns themselves with "keeping up appearances" above else and may drive a luxury vehicle, while still living at home with their parents.