Also, standard multipliers are pointless on "unicorns". You have to figure out potential for future growth and the potential of the space itself.

Facebook bought instragam for $1 billion even though there was no significant revenue or income. But the potential for growth of instagram itself and the photo sharing social media space was immense.

With established companies like walmart in establish spaces like retail, you know what you are getting. With tech unicorns, it's a bit of a gamble.

15x is modest for a virtual-product company net earnings, in cases where there are earnings after the accountants are done. A 5x multiple of revenue would value Netflix around $60 billion.

And if Walmart had the assumed 30% margins, they probably could be a $2.5 trillion company. Their revenue is more than 2.5 times their almost-$1 trillion competitor.

It depends. For a mature business like Walmart, you'd look at EBITDA, and margins to arrive at a valuation. For a growth business, especially a SaaS business, revenue might be used until there's actual earnings.