Quantity discount on 1 piece of single item

[R0BJ3]

Hi all,

Searched the forum but did not found the solution I'm looking for.

I want to give quantity discount even for 1 single product.
So, in the shop the prices are regular prices, but as soon as customer put in the cart, they get the discount. Even when they only buy 1 single item.

Why this way and why not just lower the price or give discount directly on product?
I'm not allowed to communicate other prices than RRP :-(

Anyone any ideas how to get this done?
(using PS 1.3.1)

Many thanks!