Sean proposes the following deal:
1. Buy cheap .45 cartridge rifle for -160
2. Buy cheap bayonet for -16
3. Buy 14 rations for -28
4. Buy 7 rifle cartriges for -70
5. Sell sollerets for +90 (150 * 0.6)
6. Sell cheap spear for +9 (16 * 0.6)
7. Sell 7 opioid pills for +105 (175 * 0.6)
8. Sell 14 pistol cartriges for +70 (70 * 1.0)

If they would want to alter it more than just a little, then yes, someone should haggle. Probably not Sean, because he has no practice in that.