Product Attributes

[blackflow]

Hi, I have a problem and I hope you can help:
My goal:
Im selling seeds and I come in packs of 1(5$) and 3(12$). While buying products I would like to allow my customers to choose 1pack or 3pack( and also it would be nice if the system would subtract the quantity from the WHOLE stock of seeds accordingly to the number of seeds chosen by the customer and not only form the quantity of 1(5$) or 3(12$) . Is it possible?

[enigma32]

have you tried using quantity discount?

3*5=15$, minimum quantity 3 with a 20% discount?

[enigma32]

the whole attributes feature set is pretty crummy in presta im struggling wtih it myself right now

[blackflow]

yes, I know, but I saw it done in one shop so I'm counting on doing the same. Quantity discounts are my last alternative:)
The shop I'm talking about has a seed price breakdown 10 5 3 1, all with corresponding price break down and had one quantity!