Basically for me it all boils down to, how soon do I need the part, vs cost/risk. If I need it right away, I can pay OverKill or other USA seller and get it here fast (at the premium price), but if I have the time to wait for a bit I can save money and get it directly overseas.
There is another option too though. One time I went on AliExpress, and searched for 280Ah cells USA Ship, and found a seller where they had a button (like under 'color' or something) where one selected, said 'Ships from China', but they had another button where when selected, said 'Fast Ship to USA', where the 8 cells were like $100 bucks more, but they actually shipped from Canada, and got to me in 5 days. They were still cheaper by a decent margin to USA sellers. Sometimes these AliExpress sellers have warehouses in California, Canada, or wherever, to ship faster...