Only players who own the paintball gun's Steam item can craft it. For them there is nothing to research and no bench to walk to: the recipe works straight from the inventory. Everyone else meets it only in a friend's hands.
If it is yours to craft, the metal pipe is the whole price. The metal fragments are pocket change, but before Level 3 a pipe is loot, and the same pipe makes a revolver that wins real fights. Craft the toy once pipes pile up in the box, not on day one.
Then queue a stack of paintballs and keep the gun at base for a quiet evening. It does no real damage, so it never earns a hotbar slot on a roam.
