Prices for Japan-made cells will never be as low as for chinese stuff, even if you buy them through a chines broker.
You can find comparable cells from China for about 2.5-3$. Good point about the Panasonic is their QC. Even Evvatech told me Panasonic QC is superior to Samsung QC, for only slightly higher price.
To get the price Tesla is paying, you have to order similar quantities!
Best price I found is from www.portapower.com
, but they only sell ready-made packs, for low-power applications. Their prices are around 6$ a cell, but with a good BMS and a charger. But - MOQ 50 packs!
Otherwise, if you don't trust what I'm saying, order a sample from Evvatech, maybe a 10S4P pack, and test it! Only thing I didn't like: They came with duct-tape finish... but OK inside!