LinkTrust allows you to set up incentivized sales for your affiliates through traffic caps.
From the traffic caps tab set the number of sales that the affiliate needs to reach to enter into the next pay level.
*Note: that at this point you can set up an email that the Affiliate will receive when they fill the cap, this email is 100% customizable.
Once this is set you can now find the cap redirect under the filters tab. You will need to set the capped traffic redirect to the the tracking link of a campaign with the higher payout.
*Note: that you will need to set the confirmation pixel for both campaigns on your confirmation page.