Their "caps" probably arnt even MDMA for one. For two, they are probably cut to SHIT. I bet if those people at a cap of some pure MDMA they would be on their ass for hours at a time.
Some people can just take large ass doses and be fine, for a while. It will always catch up with you though. There is really NO reason to do this, after a dose or two, you cant even possibly get any higher from MDMA, your brain wont let you. Dont follow these dumbasses examples, just stick with one or two doses in a night, no more than 300mgs TOPS.
Also test your shit with a reagent kit, you only have one brain, keep it safe.