The solution to your question is that you must get a tax id If you want the best discounts. Now there are some companies that say they want a tax id and then you find out that thier prices are total crap..
Companies like DBL and Myworldphone are larger companies and are serious only to resellers of thier products. They discount thier products according to who they are selling to. If you are a reseller you will get bigger discounts and better savings. If you are just an average person trying to buy thier items they will charge you more.
The truth of the matter is if you want to buy items inside the usa and at real wholesale prices with no middleman markup, you must have a valid tax id.