<<P3 drugs' value is built in to the stock price> By no means always the case. DNDN, RPRX, DORB - and several others on this board's list of cash-poors with P3s. Dew would argue that's because they have no chance of P3 success, but with luck he'll be proven wrong in at least a couple of cases!
Your investment thesis sounds like a version of the greater-fool theory. Nothing wrong with that in a world with many great fools as long as you recognize that sometimes you may not get away with it.