I think you should make Plat able to be gotten from VERY powerful monsters, OR....
I think Plat should be able to be gotten by killing REALLY STRONG monsters, OR purchasable via Gold, say 100 gold per ten Plat.
Superman(Because why not?) commented
Dude...ONE PLAT IS WORTH 800G AT THE TIME!
You know one plat worth of item (it can't be traded directly) is worth up to 2000g these days?