It doesn't make it "more expensive" for the Company (as opposed to its existing shareholders) raising equity capital unless the stock pays a dividend and the only way they can sell more stock is to promise buyers they won't reduce the dividend per share to compensate for the increased number of shares in issue. Tesla doesn't pay a dividend, so that isn't the case here.

In extremis, a falling/low price could limit the size of a potential new equity fundraising because the resulting dilution is too much for existing shareholders to take, but Tesla's price/valuation would appear to put it quite far from this being an issue.