Well Musk has often claimed that the cost of batteries doesn't magically go down due to big new innovations like we've seen in some other industries. Rather it's due to constant iterations, making small improvements, and economies of scale. Particularly that latter part is hugely important and hasn't been much of a factor yet in the specialised market that is car batteries. And that's why they're building a gigantic factory, because producing at scale can really do a lot to push the price of batteries down. But the notion that this is somehow unrelated to money is kind of silly, this is exactly the type of thing you could fix by throwing lots of money at it. The very reason they couldn't do it sooner because there was no cashflow to finance such a massive project.
Bingo! This reminds me of the fallacy of the mythical man month which I often compare to pregnancy in women. With 9 women, you can't have a baby any faster. The gigafactory is monstrous (second largest building by square footage in the world I believe) and is doing some quite new things. This requires R&D and no matter how you skin it, that requires time, often in serial.
