What does it mean and how much ?

that code means a couple different things it could be a faulty o2 sensor causing it to trow this code or you may need to replace your secondary air pump now that's what the code means so lets talk about what the problem most commonly associated with this type of code

with a vacuum leak you will trow this code check all your vacuum lines carefully look at them while the engine is running to make sure none of them have sucked shut or that there are no cracks in the hoses if you do not find a vacuum leak then replacing the secondary air pump could be as little as 100.00 dollars or as high as 600.00 depending on the make and model of the car give me some more info and maybe i can narrow this problem down for you and give you a better price range

i hope this helps

Not to be unhelpful, but it's difficult to determine approximate parts costs when we don't know what year and model vehicle we're dealing with. Nobody will be able to give you a price without knowing that. There is a sensor on First-Generation Oldsmobile Auroras that can go out and give you that code, but it could also be caused by badly worn plugs, leading to incomplete combustion (causing the O2 sensors to register either excessively lean or excessively rich exhaust).

Again, it's difficult to begin troubleshooting in the blind without at least knowing which vehicle you're referring to.