Ask HN: Why is Tesla stock down so much?

Yes, the broad market is suffering these days and there are a lot of macro reasons for this. Anyhow, the stock is now down almost 50% from recent heights. I know it was priced veeery forward looking but thats a valuation of only 17B at 147$ which is less then what Facebook paid for Whatsapp. Has anything changed fundamentally or is this just Mr. Market?