I feel like the big dick move here would be:
Kill another valuable monster
Show it off to the adventurer's guild under the pretense of selling it to them
Refuse whatever they offer
Say you'll just sell it to the commercial guild again like the dragon
???????????
Profit
Damn, I really liked the art style, it fit the otome theme well.
https://x.com/shiosatojyun11/status/1832796485819441390
Artist posted their thoughts in this thread in case anyone else is interested.