I say again. There are many Hobby Warehouses. Google it once and you will see a large internet store, another large one in Ca. There is only one?
If I had bought a item that was not an easy on hand item like DuBro parts and wanted to return it, I would expect a restocking fee. When they sell something the onhand supply is depleted and then another is ordered for their shelves. Now lets say that they had to order another $500 (your example) kit, because you bought the last one. Now they have none. Another one is ordered to sell and it is sitting on their shelf. Now you bring back your kit. Now they have two of them. What if it took a year to sell the one you bought? Now they have $1000 of product to sell because you changed your mind. Would you like to come up with $1000 to just have product sitting on the shelf? Would you like to go through the trouble and make the sale, get the box down, then to have to waste time and put it back? To return that part will mean that the whole time you were there, was a waste of time($) for them, and it has to be done all over again. Twice! now.
All retail companies reserve the right to add a restocking fee. To anybody. Read the company policies before buying!
To add a tick with the BBB is very easy. I am a BBB member and it is very easy to have a customer complain. It is usually meaningless. An order against a restocking fee? Big deal.