as far as I'm aware, there were no high stat clean pyrope guns to come out of the event, so there wouldn't be any "godly" pyropes in existence, let alone available to sell. You're probably better off looking for godly concertos.
Shh... Let them dream. On a serious note, @jmmainvi is correct. You'd probably have a more fun time farming up a godly Concerto or Cannon Shooter instead. You could literally make a Arch Mage and one shot Nest Golem/Dark Cornian from scratch and still make out smelling like roses instead of waiting for a Pyrope Gun.
That's easily possible for a maple canon shooter (lv 64 gun) which is a year round drop from several monsters. Pyrope gun was an event only item back during the 1 year anniversary event. Did you mean canon shooter and not pyrope? 240m would be about the right price for an 80 atk canon shooter.
a lot of pyrope weapons are much more expensive than their level 64 counterparts due to their rareness. I'd expect a pyrope weapon to go for at least double that of a similar level 64 weapon.