I live in Redmond Washington - outside Seattle - Microsoft & Amazon town. Audi, Mercedes, BMW's are like weeds here. I can say that Denali's are very much in demand as a premium truck out here. You see a lot of Yukon Denali's and a lot of Sierra Denali's. Personally I think the marketing guys at GMC know exactly who their audience is and people that shop Audi, Mercedes or BMW looking for a premium pickup or full sized SUV look to not so much a GMC but to a "Denali". I just picked up on my Sierra Denali and it is amazing how "Denali" is branded on the truck. It has become a premium sub-brand within the GMC offering. It's a great truck and importantly it is not an Escalade - which really has its own target market.
Probably they met while working at Microsoft, Amazon, Facebook, Expedia, Google, etc... A couple both working for those hi-tech companies in a mid-level jobs could afford that easily. I agree the house is a little much. That looks like a $3M house. But it is all about the aspiration... Those GMC Marketing guys are not dumb.