Um guys the fed has "printed" ~$2T out of thin air in the last five years (Fed's balance sheet increased from ~$800B to $2.9T). If we include the Fed's off balance sheet (magical money they print out of nowhere and lend to foreign central banks so for some reason it doesn't count on the "official" books) it is closer to a ~$4T expansion.
The USD monetary base went from less than 1T$ to 3T$ or I misunderstood what you wrote? Why the prices didn't bumped 3 times?
Because at the same time velocity fall off a cliff. Monetary velocity is (simple version) how many times a single unit of currency is exchanged annually. So if customer pays your employer $100, and your employer pays you $100, and you pay the grocery store $100 and the grocery store pays a farmer $100 even though it is the same "$100" you have a velocity of 4. The effective money supply is roughly 4x higher. So while the FED is rapidly expanding the monetary base the velocity is also falling. Kinda like trying to fill the bathtub with the drain open.
As someone above pointed out the FED isn't actually putting money into the hands of the people. It is putting money in the hands of the banks, who in theory should lend it out and increase the effective money supply however due to the FED other actions it is very profitable for the banks to simply borrow money from the FED use it to buy govt debt and mortgage backed securities. Kinda hard to not make money if you can borrow a (nearly) unlimited amount at ~0% and collect interest at 2% to 4%.
Ironically simply having a free "lottery" where the winner gets $x dollars on a VISA gift card which must be spent within 365 days would be far more effective then handing ever increasing quantities of money to the banks to do "nothing" with it.
So money supply has exploded but no price inflation because the money is being circulated less. However if the economy did finally pick up and velocity jumped to normal rates before the FED could soak up that excess money supply you would see massive inflation. Probably not hyperinflation but price inflation in the high teens like the early 80s are certainly possible.
To use an analogy imagine if people are cold so the FED solution is to soak them with gasoline. They still aren't warm so the FED keeps dumping more and more and more gasoline. Weeks, months go by and nope people aren't warm yet so the gasoline soaking continues, entire neighborhoods soaked with gasoline, businesses soaked with gasoline. Tanker trucks of gasoline are brought in and 24/7 spraying of gasoline everywhere continues. When the people complain "hey we are still cold", Ben Bernake's answer is "eventually there will be a spark and everyone will be warm".