Let's consider a scenario:
A championship caliber lineup: Zimmerman + Pujols + Harper + Werth. Sure, it's a little righty-heavy, but the Nats could easily pick up a lefty bat in the offseason.
Is Pujols worth $30 million/year? Yes. He's a gold glove first baseman. He's the most reliable and consistently awesome player this generation has seen. Can the Nats afford $30 million/year? Yes. (Jayson Werth's stupid contract is the only large expenditure we have on the books). Would Pujols really make the difference? Yes. Think: Cardinals + better bats around Pujols.
Just throwing it out there....