Tesla will probably never reach that price point because they're a bigger battery and more on the luxury end of things (indeed a reman engine for a German car will hit your wallet harder than a crate SBC) but there's no reason to believe that the industry will all be hard/expensive to service like Tesla and other luxury brands. Also Tesla is particularly terrible about parts supply chain and locking everything down so you'll probably never see aftermarket batteries apply downward price pressure there.