A past transaction doesn't necessarily guarantee a future price. We need to consider the following:
1. 55% Native looks cool, but it only affects the ATP of the weapon itself. Arms has pretty low ATP. (I think 140 base according to PSOW.)
2. 55% hit also looks really cool, and 5 ATA CAN make a difference.
3. Berserk is considerably more dangerous to use than Charge.
I would price it at 7 to 10.