Welcome to the world of TOD (Tens of Dollars) upgrades, they're famous on CO

Question for you - what's your fare basis? I see you are a MM, so are you CO Gold, or Plat (I think Plat as you reference it)? That will help diagnose if it's a legitimate buy-up offer (to an M fare if Plat, or a B fare if Gold), or some of the shady dealings that have been reported the past few months.

Still, it seems weird that there's only a $3 difference between an M and the next lowest fare (maybe an E, U, or H). Published fare diff between M / U is actually $195 r/t, so something seems fishy.