Discount on quantity and multiples

[nakwada]

Hello,

Posting here in hope for a solution as I have been banging my head on this for a few weeks now.

I am looking for a way to encourage my customers to buy a product in sets of 3.

For instance,

- 1 single unit costs 25 dollars
- each set of 3 units will sell for 70 dollars
- 4 units means a set of 3 (70 dollars) + 1 unit (25), so 95 in total
- 6 units would equal two sets of 3, so 2x70 dollars

I cannot wrap my head around a solution through cart or catalog prices rules, nor with specific prices.

How would one go about it?

Also, I looked but could not find a plugin that does exactly this.