Except this formula is exactly how businesses determine what operating systems, browsers, and devices they support are. They plug the numbers into the formula

Except this formula is exactly how businesses determine what operating systems, browsers, and devices they support are. They plug the numbers into the formula and see "If we block IE11 users from being able to use the site, we lose 1% of our traffic, which equates to X dollars. Is that a substantial amount? If so, we support IE11, if not, IE11 support goes out the door." So yeah, you can plug in the numbers you did and try to negate his argument, but that doesn't make his argument wrong. Just means you understand the argument but fail to accept it.