Without fighting a flame war, you could help me 
If you are convinced of this "incontrovertible fact" by first principles you could succintly state them. Say: "it's obvious that every magus needs to put at least half his xp in spell mastery, meaning FM can increase the total xp of a magus by at least 50%!".
Alternatvely -- and that would be far more convincing -- you could summarize the crucial info I mentioned above about one or more magi that you considered extremely fun/effective due to their having FM:
- Concept of magus (e.g. PeVi demon Hunter, Rego craft specialist etc.)
- Years after gauntlet of the magus.
- Total number of formulaic/ritual spells.
- Total xp in mastery.
- Any other info you deem relevant.