TheStreet.com TV Recap: S&P's Cheap Here

As much as the S&P 500 has climbed in recent weeks, it still could have room to rise, Jim Cramer said on TheStreet.com TV's Wall Street Confidential Web video Friday.

The S&P is historically low-priced here, he said. On Thursday, "the big drivers" of its leap over 1500 were selling at an average of about 14 times earnings, which Cramer said he believes is a historic low for the S&P.

"There are a lot of people who don't have a good sense of history who comment on the market," he said. "The most worrisome time in my career was when the S&P was trading at 27 times earnings, which happened to be on the eve of the crash."

That's double of where it is now, Cramer pointed out. Regarding the companies that are leading the S&P, there is a "creep up," he said. "They're at 18 times earnings, but historically they have been at 16 to 18 times earnings, so we're a little bit higher than the range." However, the earnings are coming in much better, "so perhaps the range is incorrect."

Further, Cramer said he'd go even further than what E*Trade (ETFC Quote - Cramer on ETFC - Stock Picks) and Ameritrade (AMTD Quote - Cramer on AMTD - Stock Picks) have been saying about retail investors not joining in on the recent rally -- he'd say that "the retail investors are bailing rather rapidly."

"Before I worry about them coming in, I'd like to see them stop selling," he said.

Cramer also discussed the challeges in trading this market.

"One of the things that I've learned in my career is that the toughest thing to do is to hold on in a big run and, on the flip side, to buy low," he said.

Although it can be difficult to "justify or ever redo the maximum of buy low and sell high, I urge people to look at the mechanics of the market and recognize that there is a lot of money trying to get in," he said. Market-players, Cramer said, need to widen their scale of when they want to leave the market and take profits.

Using the example of Union Pacific (UNP Quote - Cramer on UNP - Stock Picks), a stock he said he likes very much and owns for his charitable trust, Action Alerts PLUS, Cramer said normally this is a stock people would buy at $99 and sell half their positions at $110.

However, what he's recommending is that, because of the demand, investors sell a quarter of their positions. "Scale back your sales and widen your levels," Cramer said.