we dont get on it very often but have had about 450 lbs on it before... just not that often. We were aware of the 250 weight limit before buying it and were fine with that since 99% of the time its just 2-8 year old kids on it.

My guess is they are claiming 250 so the springs will maintain their tension for a long period of time whereas 300-600 lbs jumping on it everyday would wear them out much faster