It's not insanely overpowered, but it IS "better" than all of the other cheap 1H weapons like long dagger, hammer, hand axe, etc. The "stab only" mode makes it easier to not accidentally swing when you mean to stab. The swing mode does pierce damage on par with the pick weapons.
I think rondel should cost more, somewhere in the 1,000 - 3,000 gold range. It is too good for its cost, but not OP.