Wow, seems to be a lot of guestions on this subject and a lot of speculation, guessing, and probably a bit of frustration too.
As some one who has sold quite a bit of designer handbags and clothing and actually talked with the parent companies, this is what I know to be fact:
Most factories do indeed do overruns. However they are strictly not authorized. Most designer companies actually supply the materials for the goods being produced by the factories. Often a company such as lets say ralph lauren will order 500,000 shirts, but they supply much more material than needed and the factory runs off 600,000 shirts. They ship ralph lauren the 500,000 and then sell off the other 100,000 to street vendors, online purchasors and such. They are strictly not authorized to do this, but being a frugal peoples, they just do it. And in most cases they will actually make more money on the 100,000 overruns that they will on the 500,000 contract. A good example, a pair of nike shoes is produced in china for about one u.s. dollar for nike. However they will sell the over runs to an online seller for 20 or 30 bucks..
Most importantly is that in order to be legit, you can only sell 'branded' goods (designer type stuff') if you are licensed by the parent company. You absolutly must have a granted master license or sub-licence to sell their goods. If you do not then you are in violation of their copyright and trademark protection.
In addition if you purchase a branded item from a liquidator, then you have the legal right to resell that item and are covered under the 'first right of sell' laws..
If you are selling branded goods on a place like ebay and have legitimatly purchased the goods from a factory store, or liquidator, you can normally request a 'sanitized invoice' that will show that you purchased the goods from an authorized seller...I myself normally provide a photo of the receipt within my auction listing to prove that the item is authentic and purchased from an licenced and authorized seller or liquidator.. I also normally provide ebay a 'notice of intent to resell' before I go and list my branded goods.
99% of the time, its not ebay or the rights owner who reports your item and gets it pulled or your account suspended. It's an unscrupulous competitor trying to cut the competion..
Stores that are looking to rid themselves of out of style or overstocks of branded goods normally have just 3 options to dump the goods..Firstly, they discount them right in the store, secondly, they can return them to the parent company to ship to a factory store, and thirdly, they sell them in bulk to a liquidator...These are all authorized resellers...
My best advise is to only purchase goods where you can show a sanitized invoice from a factory store, liquidator, or major dept store. Designer goods are a cut-throat market and there are a ton of shady sellers out there that will take every opportunity to put you out of business if you don't take the proper steps to protect yourself....