Lit. Mgt. Mag., fall 2011 at 59, offers an example of a fixed fee for discovery: “no more than 10,000 documents to review, no more than six fact depositions, no more than two experts named by the opponents and no more than one discovery-related motion filed.” That sounds plausible to me as a basis for a set cost.
Articulated parameters such as those lay out the variables and exclude exceptional events (See my post of Aug. 22, 2011: carve-outs and two meanings in fixed fees.). Key terms are defined, or at least available for discussion, and the possibilities are addressed. They attempt to narrow previously unstated assumptions (See my post of Nov. 23, 2010: state bases for pricing.). With such specificity, the arrangement comes closer to unit pricing (See my post of Oct. 24, 2009: J&J unit pricing model.).