Here is a speculative suggestion. Double blind evaluate a few matter budgets of outside counsel and the outcomes of those matters. Follow the bouncing red ball below.
A lawyer who was not involved in the matter should rate the success of the outcome, from what was reasonably known and anticipatable when the budget was first submitted, on a scale of 1 to 10 where a 1 was a complete success. Someone else also not involved should rate adherence to the original budget on a scale of 1 to 10 where 1 came in well under budget. The ideal matter achieved its purposes fully for less than the firm anticipated at the start it would charge – a total of two. A complete mess, a matter that went to hell in a hand basket and the basket overflowed with huge invoices, would be a twenty.
This periodic, objective appraisal and quantification should be part of a post mortem on why results and costs were or were not in alignment (See my post of May 27, 2008: post mortems with 7 references; and April 27, 2010: post mortems with 7 references.).