There are sometimes sales commissions, but the CSR's main goal is to get you off the line as quickly as possible so that the next person doesn't yell at them for being on hold forever. I can't speak for Air France, of course, but I can't believe they would want to make the call longer to make 56 euros. If they quoted you 14 euros on the website, they would be most happy in the world where the software accepted your 14 euros and you never called them.

I'm guessing the original commenter just hit a bug. They should have retried some database call, but didn't in that one codepath, and it cost them the entire request. It happens.