Why C3.ai Stock Crashed 11% on Thursday

Artificial intelligence (AI) applications company C3.ai (AI -12.27%) sold off 11.2% through 10:50 a.m. ET this morning after KeyBanc analyst Eric Heath downgraded the stock from sector weight to underweight -- which is to say, from hold to sell.According to Heath, C3 shares that closed near $40 last night are actually worth closer to $29.Does C3 cost too much?Valuation is key to KeyBanc's downgrade today. As Heath points out, even adjusted for cash on hand, C3 stock costs a staggering 13.3 times annual sale ...