contribution

Well, yes and no:-) Contribution is the difference between unit selling price and unit variable cost. But it may happen that for example if you increase the level of activity (produce more) you would have to buy more materials and could obtain the bulk discount from supplier, so materials would cost less (effect of scale). In this case contribution would change as the variable cost changed due to change in activity. But if nothing changes – all prices remain the same (selling and purchases) then yes – contribution would be the same no matter how much would you manufactured.