Yeah, but there are plenty of gun/blunt melee variants. If I'm looking to dispence PvE there are enough options.
I would have to disagree that the effort is the same. A decoy skin is a single-cylindrical pattern; a rifle has multiple different surfaces/materials and places for more intricacies. The devs have some idea of value placed on their cosmetics and it has changed over time. I am considerably less likely to buy a premium Hunter if they have Legendary gear skin for things I don't use frequently. I would say the level of intricacy and any physical changes in the overall appearance of the weapon's form should play a roll in it's marketability and where it is sold and for what currency.