One more thing not mentioned yet is this:
My nephew has been a HUGE Star Wars fan from the first time he was exposed to it. And what was he exposed to, when he was about 5 or 6 years old? A Star Wars Lego videogame.
You have no idea just how popular those games were and are. in fact, they have been instrumental in saving Lego from the abyss, as Lego was struggling at the time, and these games sold like crack, pouring some much needed funds back into the company.
And until my sister decided he was old enough, and I was allowed to introduce him to the actual movies (I did it episode 1 to 6; a mistake I will not repeat with my own daughter...), Star wars Lego was all he could talk about.
He owned loads of Star Wars Lego, from smaller kits to respectably large minifig scaled B-Wing and X-Wing. Basically, it was his world.
Now, he was fairly young at the time (almost 10 years ago), but there were plenty of people playing those video games back then, who are now of an age and in the position to go out and actually buy a $800,- Millennium Falcon; the one model that always eluded them, because it was too expensive for them back then.
I'm sure if my nephew could save up his pocket money and earnings, he would dish out for one as well (let's give him another decade or so to finish his education, land a decent job and have sufficient expendable income though).
What I'm going at here, is that there are legions of (former) kids, who grew up with Star Wars and Lego (and Star Wars Lego video games) for whom a Lego set of their favourite space ship is just the most natural thing.
And most of those kids never even built one plastic model kit (and also never experienced the mind expanding effects of polystyrene cement fumes, but I digress). Because as much as we'd like to deny it, Lego is vastly more mainstream than building plastic model kits, and therefore appeals to a much larger audience.
Also, as has been mentioned; Lego is just a complete scene of its own, where spending $800,- on a set is just as accepted as spending $ 1500,- on a resin garage kit is in ours...