In my experience Necromunda is one of those weirds games where you don't so much people play it on the regular, as somebody will say "Hey who wants to do a Necromunda campaign for a few weeks?" and then people go out and buy everything for a new gang project/idea they've had (one of several usually) and then after that campaign, it will go into storage for a few months or a year, until it comes back around again.
It's not a game you see people 'pick up and play' at their local, there's almost always a more organised effort around it - in that respect it's not far off a DnD campaign.
From what I've heard it is a good seller.