Okay here's how the prices work.
Usually 2 weapons= a scrap, unless someone wants a specific weapon from you, which is 1 scrap for that one weapon.
3 scrap= 1 reclaimed, meaning 6 weapons. You have 7. This means you have 1 reclaimed and a scrap. (or 1/2 of a scrap)
3 reclaimed metals = 1 refined metal. Refined metal is worth 3 reclaimed metals, 9 scrap, or 18 weapons.