It all depends on the nature of the test pressing. Some labels test press acetates and these are more limited, and degrade quicker with play.
Most companies nowadays print up to 100 copies as test pressings to send to artists, management, companies for air play. Older test pressings were more limited in copies pressed.
Main artists such as Elton John, Queen, Zeppelin, Stones, etc, will always commands higher prices than lesser known bands.