THe price difference between the no-name frame and the de rosa is likely to be significant... if the Chinese company is the manufacturer of the frame then their wholesale cost to sell to De Rosa is going to be a small fraction of the De Rosa bike cost. I would guess 10% or less. But that is the way business works. If you buy a new electronic component for your Chevrolet it is considerably more expensive than buying a bunch of diodes and resitors and connectors.
You are not paying for just paint and a name - you are paying to weed out the junky or irregular ones, a domestic warranty service, assembly, etc. I'm not saying it is or isn't necessarily worth the money, just that the difference between the unit cost on a Chinese frame and the price of a very similar brand-name frame is not the only factor.