Test Stations can be useful for two very good reasons. First they allow bulls to get more exposure than is generally possible than if they are fed at home, especially if you are a smaller or new breeder. The first bull I station tested topped the test and sold for a good dollar to an Ontario breeder. He would never have been found If I had fed him at home. Secondly they allow you to compare your bull production to other breeders relatively independant from management or "fitting".
Not all bull test stations feed high forage rations (eg. Douglas Bull Test in Manitoba) and yes they can be expensive. This must be weighed against the potential benefits.
Good Luck!