Guillaume commented on Inventory Problem. Need a friendly help ;-)

Thank you very much for your time HJ.

I just found an App called "Quantity Breaks" to manage my "Tiered Pricing" problem (didn't know it's called like that in English).

It's not for free but it might do the job.

Here is a link to the App for those who will have similar needs :

https://apps.shopify.com/quantity-breaks

The "Product Bundles" App could also help.

https://apps.shopify.com/product-bundles

I'll try both of them and see if it solve my problem.

Guillaume