Average P/E across all business sectors tends to be around 15 long term, with fluctuations mostly staying between 10 and 25, getting out of these ranges only in extreme cases like a war or a major international crisis (in XX century, U.S. average p/e was under 10 for any significant time only during WWI, WWII, and the 1970s oil shock). If some business is really worth only 3x of its annual profit it must be a really, really dodgy one (only one of the hundreds of tracked business sectors with P/E under 3 now is TV broadcasting, which is agreeably on its death track).
A company’s valuation multiple can be highly sensitive to the choice of denominator. You are making an apples-to-grapefruits comparison by trying to equate “seller discretionary revenue” with US GAAP net income per share.
The SDR calculation [1] excludes compensation and looks like a generous net revenue measure. Earnings per share -- from which P/E multiples on public companies are typically calculated -- includes compensation, interest expense, various non-cash adjustments, and adjustment for dilution.[2] Generally you would expect the SDR number to be higher than net income and correspondingly attract a lower multiple in estimating firm value.
As others have commented, there are additional reasons why valuation metrics for large-cap listed companies don’t make for useful comparison with SaaS startups. See also Heidi Roizen’s cautionary tale [3] about the perils of multiple envy.
