An item with no warranty simply means that you are responsible to pay for any work that may need to be done to fix a product. By the time you pay to get it fixed, buy a new one, or both, you will end up spending more money and certainly more time than if you had purchased a legitimate product in the first place.
Need proof? Call any of the companies directly and see what they say. They usually have it plastered all over their warranty page about unauthorized selling. Don’t be fooled into thinking they won’t know: manufacturers track every serial number on every product. When they see that it was purchased from a non-authorized seller, the warranty is completely void.