I think op just meant that they do bad work for exorbitant prices. And gp showed some of the pressures that can drive firms to buy optional services from consul

I think op just meant that they do bad work for exorbitant prices. And gp showed some of the pressures that can drive firms to buy optional services from consulting firms: desire to maintain a "good relationship" or possibly just discounting and bundling. Also, the big consulting firms are generally known for aggressive upselling. It's often a core part of their business model. Once you've got em on the hook... So, TLDR: Not shakedown as in extortion, shakedown as in bad service for a bad price.