Volume Discount + Discount Stacking special requirement

[Danson]

Hey guys,

after weeks of research and also consulting with some others, I now have to fall back on your expertise. I've been working with Shopify for about 3 years and I keep coming back to the same problem.

What I need:
A quantity selector on the product page with a dropdown field that already calculates and displays the quantity discount.

See image

In a nutshell:

I need a solution for the volume discount problem. In our store we sell single cans and also offer discounts for larger quantity: 10, 30, 50 pieces. (Across the industry volume discounts are very important for this type of product).

Currently we use the app "Selly" to solve our problem as it allows us to offer volume discounts and discount codes at the same time. The app works fine but it still has a few disadvantages, e.g. additional discount code is only calculated in the checkout (lots of customers oversee it and abandon), slows down page loading time and in addition, our store is highly customised and we always have to contact our developer when changes are made. Also we want to add a quickbuy feature on our collection pages (for quantities) which only works with variants.

Example Quickbuy feature:

Isn't there a simpler and more effective alternative?

I also had the idea of offering the quantity discounts as variants, but the problem here is that in the shopping cart and in the checkout a 10-pack is displayed as 1 piece and not 10 individual pieces. In addition when a customer adds 11 units to their cart, the 11th unit is full price and not discounted.
Is there perhaps another approach?
Is it at all possible to insert the quantity discount directly into the theme?

Thanks in advance for your help!