different prices for same product

We are selling a product where the first subscriber would be billed X amount, and each additional subscriber would be billed X - Y. In an ideal world, the customer would select, say 4 subscribers, and the cart would show one at X price, and three at (X-Y) price. Sort of like a "buy one, get one at half price".
Can this be done? If not, what is the best solution?

I think that you can do that with AXO Coupon:
awodev.com/product/awocoupon-pro
awodev.com/blog/buy-x-get-y-joomla

With HikaShop directly, you can't do that directly and you would have to set unit prices one per quantity which would be the calculated average price.
So for example for two products the unit price would be (X+Y)/2 and for 4 products, the unit price would be (X+3Y)/4