As measured by the median S&P 500 stock, the price-to-sales ratio is even higher, at 2.7 times currently. By contrast, the median S&P 500 stock traded at 1.2 times sales back in 2000, far lower than the cap-weighted 2.3 times. Bottom line: The average stock now is valued more richly now than in 2000, when a relatively few kooky dot-coms distorted the market’s overall measures. https://www.barrons.com/articles/stocks-are-pricier-now-than-they-were-in-the-dot-com-era-1536836400
I totally disagree with this, quoted from the Barron's article in that link you posted... "...Contrary to the conventional wisdom that things aren’t nearly as nutty as back then, he sees markets as riskier now. There are parallels between the concentration of gains in the FAANG stocks— Facebook(ticker: FB), Amazon.com(AMZN), Apple(AAPL), Netflix(NFLX), and Google parent Alphabet(GOOGL)—these days with the internet stocks around the turn of the century. But what’s supposedly different this time is “today’s Technology titans are ‘real companies’ with massive revenue underpinnings—rather than page clicks and eyeballs, as during the original Technology mania,” Ramsey writes in the firm’s monthly report to clients, known simply as the Green Book to its fans for the cover color..." The author fails to remember that back in 2000, there were no smartphones, the Internet was still the wild-west with fluid standards fighting for recognition, and hell, the "mass-market Internet" was still operating mostly on dial-up and only ~5-7 years-old at that point. Here we are almost 20 years later, and the Internet is way more evolved since those "heady days". That is why they were "heady", because it was all so new, so unknown to people. Those days were the very definition of the term. The FAANG companies today are far from "heady". We have a whole generation of people now who grew up with these companies from birth, and consider it par for the course, "just the way of things." It has become normalized. Remember, this all happened because of the rapid expansion of broadband Internet across the world. Without broadband, NONE of this would have been possible. Not to mention... The original "technology mania" may have been driven by "page clicks and eyeballs", but now companies like Google have invested infrastructure in, and are profiting greatly from, new technologies that were not around back in those days, like cloud computing and storage, thanks to broadband that has now become way more affordable and made sense for businesses to adopt. Stuff like that is huge now.
In other words, this time is different? - Quote near the dot com market top. Although this Bull Market probably has a ways to go, there are some serious clouds on the horizon. These clouds include Demographic challenges with the aging of the large bulge in population in most developed countries known as the "Baby Boomers". As people age, they tend to spend less and they will eventually become net sellers of assets, including stocks, real estate, and collectables. In addition, many Millenials are not interested in buying real estate. They are happy with their apartment in the city and ride sharing. Most of us know about supply and demand, right? Consumer, business, and government debt levels are at all time highs. Many households in high priced real estate markets are about one month away from being late on their mortgage should they lose their primary income. A recession could easily snowball into something worse. The products being released by several prominent companies such as Apple and Tesla are no longer impressive. Apple's latest iPhone iteration features a nicer display and not much else. Cheaper smartphones exist with better features. Apple has also decided to not upgrade their popular smaller phone. I own one of these phones and when it dies I will literally go to a $18 flip phone and an iPad. There are also privacy benefits with my flip phone idea, especially starting in 2019. Tesla probably will never become profitable. Viable battery technology, such as a doubling of energy density, is probably a decade or more away. Although TSLA stock appears loosely correlated with energy prices, the overal cost of ownership of a Tesla versus a basic gas powered car was a long way to go before it is competative. Tesla does have some snob appeal, I suppose. Bottom line is don't get too comfortable in this Bull Market. Depending on your time frame and trading skill, start thinking about risk reduction and wider diversification of your assets and income streams.