Again, why not ask them? You can be a real dick sometimes ton. You're asking us why someone else has done something we're not involved with.
It could be that one has a surplus of stock they're willing to sell at cost. It could be one has a discount scale in place. It could be that one has made a mistake – be it maths or component. It could be that one was given a wrong price by their supplier. It could be one of them is being evil and trying to rip you off to further their plans of world domination.
Honestly, why is your first choice to resolve this query is with a third party and not with those providing the prices?