It's definitely a dick move as a dm, but it adds a little depth to the go kill X kobolds at Y location and the gold is moot because i plan on making them lose it all in the end as a plot twists. The military will provide them with basics for next adventure.
I guess I can possible have the daughter fail. Maybe the guard will get them for the murder of the rogues when the governor goes to confirm the extermination and collapse the dungeon.