Well, that's putting the best construction on it.
What he means to say is, Most assets are dearly priced.
Dollar cost averaging into stock index funds right now is buying at very high prices with the Shiller p/e near 20, when the mean is more like 16.
Oil is about $80 per barrel vs. $20 in the go-go days, gold is $1,586 the ounce vs. its last peak of $800 in 1979, and the price of the Vanguard Total Bond Index is at historical highs around $11.
People who own these things are nervous because the prospect for considerable increase in price is improbable, for various reasons. Some wonder when to sell. Many more have bought and will hold as they have been taught to do. How many people do you know who ride it on up, and ride it on down? Well, can you afford to do that facing retirement? What if the next leg down is really big? Let's say a retest of the 600 region of the Standard and Poor's 500 Index, and we bump along down there like Japan for another seven years.
People who don't own these things are also nervous, because what they do own, if they own anything like cash and real estate, is declining in value and is returning nothing. They wonder when to buy the other things, and don't especially believe it when people like Mr. Bogle tell them they've got to invest in the markets at these prices.
What would you expect him to say, under the circumstances, Don't buy my funds?
He sells good stuff, but maybe you should wait for a sale, and be patient with what you do have, and try to find a way.
Read him, here.