How to add a fixed starting price to unit pricing?

[Omikai]

Hi
Im looking for a way to price a product using a fixed price + a unit price
There are several different plugins that helps me to add optional pricing to the unit price so that is not a problem.
But the unit price is then always multiplied with the quantity.

I want to add a fixed starting price to the multiple.

Example:

The product cost 10/piece

I have a fixed starting price that cost 100

1 piece should cost 110

2 pieces should cost 120

and so on

The fixed starting price is for handling the order in production.

I have tried various plugins but all the time the new unit price is multiplied with the quantity

I have tried various plugins for volume discount to add a discount to the cart to come down to the expected new price but they are always having a limited number of tiers. 

But I need to find a way to solve it if when the quantity is 1 but also when it is 1000

Anyone have a solution for that?

[MastersHub]

Do you have a Shopify Plus plan.