Unless we're willing to buff other aspects of it, DMP isn't in the same tier as Randuin's Omen and shouldn't be costing 2900g. Just like Sunfire's cost was lowered from 2900g -> 2750g, so should DMP's. It's an item that is meant primarily for mid-game so it needs to spike faster. IBG is in a similar spot and costs just 2700g.
I think part of the reason it's overpriced is that it's often bought later and combined with synergistic items such as Trinity Force. However, not every DMP user can benefit from such synergies so they shouldn't have to pay so much extra for an item like this. It's akin to having X item being good on 4-5 champs and thus nerfing it for all potential users to keep those in line. If it's considered that the current iteration would be too good at 2750g (unlikely imo), perhaps it can have a bit of per level scaling on its MS so you don't get the maximum benefit directly on purchase.