There is truth in seeing past the name on the downtube. You are paying for a name so you can get good deals by not buying from the major brands. One thing to know is the brand Motobecane is owned by bikesdirect.com (along with Mercier, another famous French cycling brand). So part of the saving comes from distribution (or lack there-of to local shops) and being a house brand they skip at least one level of markup.
Also, the fact is there aren't actually that many factories in Asia that make most bike frames and some components. A majority stake of Specialized is owned by Merida in Taiwan, which one of the larger OEM for other brands along with Kinesis, Giant, Ideal, etc. AFAIK Motobecane bikes are made by Kinesis in Taiwan.
Coming from the same factory does *not* mean it is automatically the same bike. An OEM will make as good or poor of a bike as they are paid to do. The contracting company has a target price, performance, quality specification. If that price doesn't allow higher end material or sufficient QC it's no sweat off the OEM's nose since it's not their name on the warranty. Santa Cruz bikes, which are high quality, are also made by Kinesis (at one time in Portland but Santa Cruz frames are made overseas now). No one seriously familiar with the bike industry will claim a Motobecane is the same final product as a Santa Cruz. The quality of the frames are different but the total package is on the shop floor is completely different leagues.
It's also true that a 2nd tier brand has different cost and profit requirements so you can get a bike that costs something less than a major brand while being just as good or better. But it's also just as true that a brand like Specialized has a heavy burden in the reputation of its name. That's all it really has since most companies don't own much physical production capacity so their value is in marketing. Motobecane is just a name and bikesdirect.com will find other well known cycling brands if Motobecane is ruined. It's the same case with Schwinn, GT, Diamondback, Bianchi, Fuji. Just names owned by investment groups.
Personally, I agree with Christophe about Motobecane. They have slipped significantly in quality. Doesn't mean I wouldn't buy one or recommend them to someone who had a budget because some models are in fact high value. OTOH Specialized makes both high and low end bikes and their low end bikes aren't the same quality either. So the "You get what you pay for" statement is about as universally true as anything. A $700 Motobecane is probably going to be about as bad/good any other $700 bike out there regardless of the name on it. The main reason I'd stick with Specialized (as an example, I wouldn't support Specialized for other reasons) is after sale and warranty support. That's what you're paying for, having someone to call if you have a problem.