Pfizer (PFE) is undisciplined.The drug giant is paying around three times what Medivation (MDVN) was worth just six months ago. Like Microsoft (MSFT) over-bidding for LinkedIn (LNKD), thanks to Salesforce (CRM) making competing bids, Pfizer is paying top dollar for the cancer drug maker.Pfizer ought to have learnt from Gilead (GILD), whose $11 billion buy of Pharmasset in 2011 will go down the MBA history books as the buy of a century. Having a treatment for Hepatitis, Gilead acquired a moat. For Pfizer, it is betting Xtandi sales of $595 million in the second quarter is just the baseline. The treatment for prostate cancer costs over $100,000 per year.For a mere 11x sales, Pfizer thinks its acquisition is a smart one. If the company is wrong, shareholders will pay the price.Seasonal strength for biotech will keep Pfizer’s stock elevated, but as the sector floats higher, set lofty exit prices.