If the lawyer predicted that the court would block discovery on the XYZ issue, which the court then declines to do, not only is the lawyer going to have to explain the new discovery expense, but seeds of doubt about the lawyer's judgment have been planted. Estimates do constrain the lawyer's fees, but within boundaries set by the lawyer's own expectations. Estimates thus make managing the lawyer easier for the client. The client need not speculate about what to expect or how much it should cost once the lawyer, who is supposed to be an expert in the field, creates his or her own roadmap. The estimate also makes fee management easier for the client by placing psychological pressure on the lawyer to avoid breaking the estimate.
Lawyers often discount fees before sending the bill, to avoid confrontation with the client.
Exceeding Estimates Aside from the subtle psychological effects of the estimate and underlying plan, there is nothing subtle about the direct effect of exceeding an estimate. Once a budget or estimate has been communicated to a client, the lawyer has a continuing duty to update it, especially when new events make the old estimate misleading. The consequence of exceeding the estimate can be disallowance of the extra fees or a substantial portion of them. These agreements also provide that any changes to the estimate must be approved by the client. At first it might seem to be in the client's interest to accept a low-ball estimate, to save the money.