I did some investigation of VirtueMart 1.1.x discount system and the first thing I did notice is that VirtueMart 1.1.x does not support progressive discounts natively. In other words it does not allow to define the discount based on the amount of products bought or total amount of money paid.
There is some useless discount module that “Generates a discount in % of subtotal in virtuemart-cart.”. It installs fine and provides a simple settings page:
but it keeps refreshing very frequently showing “Please waint…” message and slows down the entire web site:
I think, VirtueMart team is planning to “Add more different kinds of calculation (quantitative discounts, progressive discounts, profit)” in future releases. Probably it makes sense to wait for VirtueMart 2.x.