Airlines suck.
On the other hand, the few times we travelled with him with children he would buy one seat and my children, who probably weighed less than 50 pounds sat next to him and they were all fine, having the entire row.
But I can tell you the way the airlines treated him at times lost them a lot of business— he bought two seats when necessary but would rather drive 1000 miles then put up with them. And if you’re going to charge by size/weight most of my family deserves a discount because they are smaller than average, not just the one that is larger paying more.
“That’s what she said.”