I don't know where you shop mate but take a look at the real world.
They are not exaggerated at all. The outputs are guaranteed and if they cannot achieve the rated output under standard test conditions you can get your money back. However the test conditions are generally not representative of the real world. The rated power can only be obtained with 1000 W/m^2 irradiance while the panel is at 25 C. That is equivalent to aiming perfectly at the sun on a clear day while the panel is somehow maintained at 25 C (which will be difficult on a clear day, unless the panel is in a cold place).