Can depend on whether that 200 watts is an RMS wattage vs. PEAK wattage. Also a lot of cheaper brands overrate their products. Could also have to do with impedance not matching properly (i.e. hooking 8 ohms subs up to a 2 ohm stable amp for instance will not be as loud as lower impedance speakers)
Could also be under-sized wiring, the box that the subs are in, whether the boxes are ported or not, as well as the general acoustics of the vehicle, some cars are better insulated than others.