Estimating that Cisco paid 10X revenues for Duo is certainly possible I think. But the range may be as high as 23X revenues if you base things more closely on the numbers in the news pieces below. Where the price to earnings number was at the time of the Cisco buyout I don't know.

I think the multiple for SFOR will eventually be quite high due to the very low overhead of their business model.

I believe that most companies in the current round of infringement lawsuits saw their potential financial risk climb dramatically as the USPTO supported the SFOR patents in October 2017. Additional cases at the SCOTUS, Court of Appeals for the Federal Circuit, and elsewhere may have potentially reinforced the financial risk of the companies that SFOR has taken to court. I think their owners may potentially have considered these factors. I wonder if in a part of their calculations to sell their companies, they have been motivated to de-risk their potential liabilities and cash out to much bigger corporations which could handle the potential liability. They seem to have found ways to cash out IMO and it is intriguing. These are just my opinions.

Here are some tidbits about Duo

On February 1, 2018 Duo posted that they had exceeded 100 million in annual recurring revenue.

October 1, 2018 Cisco closed that deal for $2.3 billion

https://duo.com/about/press/releases/duo-secu...innovation

https://www.networkworld.com/article/3310198/...m-duo.html