Dealers cut powder drugs such as heroin with cheap inactive fillers, basically so they can make more profit but making it look like more, so no heroin on the street is 100% pure. 50 times is a bit of an exaggeration though, that would mean that the heroin was only 2% pure, which would be very shitty heroin.
Opium is not the main ingredient in heroin, heroin has no other ingredients aside from the fillers found in street heroin. Heroin is just heroin, it's a drug synthesized from morphine, which is isolated from opium.
I don't see what could be good about heroin being able to be cut so much without people being able to tell by looking at it, unless someone is a cheap dealer who likes to rip people off and doesn't have any long-term business sense. From all other perspectives - drug users, harm reduction - it is a very bad thing that this occurs, since one can never know how pure the drug is until you use it, which is both dangerous and frustrating.
Anyway, this thread isn't really suitable for Basic Drug Discussion but I thought I'd answer it before closing it. Please PM me if you have any concerns.