who has experience with cost reduction consulting firms

Hello!

Anyone have experience with cost reduction consulting firms? I know many of these firms focus on procurement (i.e merchant fees, shipping, telephony, etc). I am more interested in firms that focus on change management/operations (org structure, etc) but are not traditional "strategy" firms

Seeking info around contract terms - mostly focused on how they price themselves - % and term length, etc. I hear pricing can be contingent and based off a % of savings.

Happy to have offline conversation.
Many thanks!
Jason