Too bad no US sellers yet. But you know all DJI drones and all accessories all come from China.
Some of those ebay sellers from China partner up with some US sellers and ship things to them to have on hand. You know buying from directly from them in China is cheap, though it takes long for you to receive it.
If there was a US seller, I am sure he may have to sell it more expensive. be realistic and imagine how much such a huge thing would cost him to ship to you. Then ebay fees on him. Then imagine at the end of the year when he has to file taxes on those goods. Then also imagine that he is selling the product to make a gain. How much gain do you think he may even make? Zero. So not worth it to have a US seller.
Selling on ebay is not easy for some US sellers. That is why, I just buy from China and sit and relax. Your product will finally show up. Since there is no other way. Except you want to buy US made products which have to be more expensive most of the time.