NO! NEVER buy expensive mods to attach to a weapon you KNOW you're going to sell. If you have say a + 29 hp mod laying around, you can choose to put it. But shelter isn't that bad actually, especially for melee ppl, like warriors and sins. But never buy expensive mods for a wep just to make it higher in price, cuz it probably won't sell for more. At least not as much as you paid for the mod.