I don't see BD as trying to sell lower quality bikes as higher than actual quality. I see their bikes as options with a pricepoint that is typically lower than similar spec'd LBS offerings.
Using your example, the Motobecane Gran Turismo isnt listed as just DuraAce.
DuraAce/Tiagra/DeoreXT
Touring CrMo Bike
Motobecane
Gran Turismo
SALE $699
It shows Tiagra and DeoreXT as well right there on the main page. And if you click on the bike, the components are clearly listed. That sure doesn’t seem like an attempt to make it seem like the bike is all DuraAce.
And after looking at the components, I would say that is actually quite a nice stock setup for the money. I know I wouldn’t find anything comparable in my area for that price.
I completely agree with you on not having a chance to try the bike out. That could be a negative. And if someone isn't able to put the bike together properly, then they will need to pay for that service, which eliminates some of the savings. But still, its cheaper than anything I would find around me with those specs, even after paying another $100 for an LBS to assemble.
As for buying local and supporting regional shops- that's an ideal, but I don't see it as so important that its a top priority. Panniers I bought a months ago were $25 more locally. The rack was $10 more. 2 rims I am working on were $12 more per rim. Tires- well tires are just nuts I don't even try anymore. Bar tape is consistently $5-10 more than online.
etc etc etc.
Ive picked up some tubes, a kids bike seat, and a freewheel tool from a few local stores in the last few months because the pricing is similar or I just want the item right away. Other than those two reasons, its tough to justify the prices.
Oh, I did by my spokes locally since they figured out the lengths. That was $50 more than online. $50!! For 72 spokes! But they did do the calculations and more important I knew they would be correct vs an educated guess on my part.