If you are looking to integrate the RealSense cameras into a product, then the USB cameras can be used for prototyping. For the final product though, I would recommend using the caseless 'Depth Module' circuit board version of the cameras. You can use these in a commercial product, whereas the cased USB cameras are not recommended by Intel for this purpose because they have a limited 90 day warranty.
If you want to source the Depth Module boards in limited quantities then you could order them from a company in your country that is an Intel Authorized Distributor. If you want to source the parts in large quantities (e.g 50,000 +) then you can open a sales inquiry ticket with Intel.
You can learn more about the module boards for the latest 400 Series cameras by going to this page and clicking on the 'Depth Module Specs' button about two-thirds of the way down the page.