System: Life As Arms Merchant In War Zone

*Could you imagine what would happened when the Modern weapon caminto the medieval cultivation world?
As an Ucg nerd He had accidentally came to this Isekai continent with the Arsenal System. 
In this world, Demons, elves, humans, and cultivators wereat war...
Some people for survive...
Some people for their own benefits...
It had made this war never going to be ended. 
As for him,Thanks to the system he became the weapon dealer wandering between them! 
What, you want two machine-guns?
Five hundred thousand demon gold coins.
You still want the flaming cannon? Fine, but the other side gave him five hundred thousand gold coins. 
What, you gave me 5,000,000 gold coins!