iTravel makes it easy to group your subagents by markets.
For example, create a Gold Partner Market where the prices are 20% off and a Silver Partner Market where the prices are 10% off. Group the subagents that buy of you the most into the Gold Partner Market, and the ones who buy less into the Silver Partner Market.
It is possible to assign as many subagents as you need to a certain market. This will allow those subagents to buy from you at that market price.
Add a single subagent to more markets. The best price will be given to the subagent.