As stated before , if no market for that , then no one will do it = when have you seen history paying off in such way ? If providing such data would make someone rich trust me dozens of players would pop-up and airlines would love make a piece of it

As IrishGuy said , you need to study to recognize if a deal is a good one and i would , as you are an AMS based flyer , ask you to remember that KL has little incentive to offer competitive prices as they are the sheriff in town and see you as captive customer , quite often i seat on same flights as ducth KLM customers and they are shocked to see how much less i paid compared to them by starting from central europe

So check similar competition (please compare apples to apples only) on same routes for a long period of time and then compare with next big KLM sales to know if KLM is lying or not (spoiler alert = its not urban legend , just business 101)