Discount when 5 copies of the same product are purchased

Hi,

So, reading between the lines, I suppose that you also want that:
- 5 x productA = 100€-10% = 90€
- 5 x productB = 150€-10% = 135€
- total = 225€
And also:
- 1 x productA = 20€
- 4 x productB = 120€
- total = 140€
And also:
- 6 x productA = 100€-10%+ 20€ =110€
- total = 110€

Which means: the discount quantity threshold is per product, and the discount can be cumulated with different products of that same category in the cart, and the discount quantity threshold is by steps of 5 and the discount doesn't apply to the products in between the steps.

Combining all this together with what you wrote in your message means that it is difficult to achieve everything with the discount system or the coupon system or the prices system or a combination.

With coupons, with the "auto loaded in cart if possible" setting activated, and product A selected in their "products" setting, and with min / max quantity, you could configure a 10€ coupon, a 20€ coupon, a 30€ coupon, etc so that the system could switch between the coupons of product A based on the quantity of product A in the cart.
And you could configure similar coupons for each product.
However, since the coupon system only supports 1 auto loaded coupon per cart, you couldn't have a coupon from product A and a coupon for product B at the same time in the cart.
You could have the users manually enter coupon codes so that they would be able to add several coupons to a cart (with the multi coupon plugin in our marketplace ).
But it would still require the creation of a lot of coupons. And you would have to provide the codes for each product to the customers. Not ideal.

With prices, in each product you could configure several prices with different "minimum quantities" and adapt the unit price to match with the total amount divided by the quantity. That would require creating one price for each quantity of each product, so not ideal either.

The best would be to develop a small plugin to calculate the discount dynamically and add it to the cart as an "additional fee", similarly to what we did with the global cart fee plugin:
www.hikashop.com/marketplace/product/224-global-cart-fee.html
That way, you don't have anything to manage once the plugin is developed. But it requires a bit of initial development.