We offer every publisher personal rates.
We are currently investing in our tube sites, growing them by buying all and any traffic from publishers to our own landing pages. This is why we buy ALL traffic, even non unique.
So, your rate would be calculated like this: Your rate = Everything we earn from your traffic * Personal Multiplier.
Minimal value of personal multiplier is 1, usually it is between 1.2 and 1.5 so in other words we pay 120-150% Revenue share. As a starting bonus we will set your multiplier higher, then our system will analyse your traffic quality (such metrics like uniquness, bot %, clickrate, bouncerate) and profit.
As you can see, rates are not fixed and they have never been stated as fixed. Perhaps the quality of your traffic changed and that is why your rate has changed as well. At least this is the most common reason of rate changes.
If your traffic is undervalued or if you have other questions related to this, please, don't hesitate to contact us.