For $150, I am guessing it is the Horns ONLY. You then need to add in a compressor, pump, lines, fittings and switches.
If it is everything, then I would ASSUME it is junk. Good pumps are more than $150 alone! Also, Tank size DOES matter. The bigger the tank, and faster the pump, the longer, and more frequently you can use them.
If the tank is < 5 Gallons.... you will NOT get long horn blasts... PERIOD!
KillJoy