Crate & Barrel is the American, mid-priced, moderately upscale furniture and home decor chain. CB2 is Crate & Barrel's less-expensive, urban, hipster, online version. Whereas Crate & Barrel might offer a classic leather sofa for $4,000, CB2 will offer a more contemporary vinyl version for $2,700. Think of it this way: if you're looking for a solid oak butcher block table you go to Crate & Barrel. If you're looking for tiny, lime green, square, glass serving platters you go to CB2.
I am almost completely certain neither Crate and Barrel nor CB2 are mid-priced. Using your own example, both a $4000 sofa and a $2700 sofa are quite expensive, even by U.S. standards. I would classify a mid-priced sofa close to $500, and a low-end sofa close to $200, and yes there are many, many stores which can supply sofas at these kinds of low-and-mid range prices.