Are marijuana stocks ridiculously overpriced?Of the top three marijuana stocks in terms of market cap, only Aurora Cannabis (NASDAQOTH: ACBFF) reported positive earnings over the last 12 months. The stock's price-to-earnings (P/E) ratio currently stands at a whopping 488.We can't use P/E ratios to assess the valuations of Canopy Growth (NASDAQOTH: TWMJF) and GW Pharmaceuticals (NASDAQ: GWPH), but we can look at another commonly used metric -- the price-to-sales (P/S) ratio.