TimeOut

As far as polycarbonate shells, almost all of these brands have similar polycarbonate Makrolon (R) material.  And are sourced and are generally produced in the similar methods.  It's about the other minor features that are added to each one of these.  Think of the watch industry...  Almost all the watches have a generic movement from a generic supplier from ETA, Sellita, SW, etc.  

White label Chinese factories already have a whole sales team ready to work with your design team.  You choose what you want.  They'll source the interior.  They'll give you a rough template.  They'll source the wheels.  And they'll offer you some creative ways to make your generic white-label product into something more customized that looks completely original to the average consumer.  

So, I could make my own suitcase; Makrolon shells with a leather accent, the highest grade YKK zippers (or go clamshell design), a cool lock that my team works with a hardware line to make, a cool interior, source the Hinamoto wheels from Japan, have it all made in China or Vietnam by a contract manufacturer that already specializes in suitcases.  And just order them by the shipping-container load.  

Then, look at Tumi.  Tumi does make a great product, they're owned by Samsonite conglomerate.  But the products are made in Samsonite contracted factories - just to a different product quality level.  Imagine your Audi/Porsche being made by VW's factory.  And then it's more brand engineering rather than real engineering.  The VW version gets the standard suspension and smaller brakes, and a plastic interior.  The Audi version gets a differently tuned suspension, bigger brakes, and some plastics are replaced with nicer materials.  The Porsche gets a sportier suspension with air-ride, more tech, biggest brakes, etc...  And they're all made in the same factory.  At one point, demand for a particular Bentley was so high that VW's Phaeton plant had to be converted to make the Bentleys since Phaeton models were not in demand.