Earlier quoted context omitted.
Khan Academy has an amazing collection of videos on finance. I highly recommend it for understanding cash flows, enterprise value, etc. It's helped me transition (one foot out the door) from tech to finance.
Any other good sources, like books or articles ?
The average price to sales for S&P used to be between 1.5-2.5 for many decades. However for these newly IPO companies the price to sales ratios are around 10-15.
Similarly the P/E ratio for S&P companies used to be in the 15-25 range to the considered normal .
However with these internet companies, they usually do not turn a profit or if they do, their PE ratios usually lingers in from ~100 to 1000. And the market considers that normal behavior now.