And aimed at collectors, not kids with lame parents.
I don't follow Lego closely, but I'd say that the sets that are directly aimed at collectors are the modular buildings, which they release about one a year.
The 'pop culture/licensed stuff' is probably largely aimed at adults, but Playmobil has started doing that now (the Ghostbusters and Back to the Future sets), but I class those slightly differently. I'd also say the museum figures, and stuff like that is aimed at adults, and I think that's a market that has potential (since a single klicky is cheap, and light and small).
I suspect that the production model of Lego makes sets for adults easier to make (I could be wrong, but I think the designers of early modular sets were only allowed to use parts and colours in production elsewhere).
We obviously don't know the figures, but even sets that were super rare/expensive on eBay end up being sold off at a reduced price via Direct Service, which would indicate that the adult market isn't huge.