The same could be said of much of today's corporate bond market. Other recent standouts, according to FTN Financial's Jim Vogel, include Caterpillar bonds due in 2064 trading over 114 cents on the dollar, Mayo Clinic 2042 bonds at 115,Microsoft bonds due in 2055 going for more than 117 and Bristol-Myers Squibb 2097 bonds going for about 150.
Also remarkable was the way corporate bonds recently traded amid the panic over Britain's vote to leave the European Union. Typically in a panic, corporate bonds sell off as investors fear weaker growth, tighter financial conditions, or need liquidity.
Instead, corporate bond prices have risen since that vote, such that the yield on the Barclays aggregate investment grade index has dropped another 0.3 percentage point to below 2 percent.
"Rather than a specific bond, I would say the entire investment-grade universe is egregiously overpriced," said Reynolds. The bonds "look awful on a risk-return basis."
That's not to say parts of the stock market — like utilities, in the same grab for perceived safety and yield — aren't out of whack too. Indeed, the utility sector has quickly mushroomed into one of the market's largest.
But the same was once true of energy stocks during the commodities bubble — and the S&P 500 not only absorbed that body blow, it is on the cusp of breaking higher.
In fact, the index has returned 4.3 percent annualized since January 2000, with dividends reinvested. That period encompasses the dot-com crash, the housing crash, a global financial crisis and the commodities crash, to name a few.
The more bond prices keep surging, the likelier it may have to absorb a bond crash, too.