The "usual" hourly fee rate of attorneys in the jurisdiction" --is a statistical market rate determination. Most courts require the reasonable hourly fee award amount to be based on the "usual hourly fee rate of attorneys" in the court's jurisdiction.
Most so-self-proclaimed fee experts skip discussing the "usual" rate because they don't have data. Those fee experts who do discus the "usual" rate in court often base their summary of the usual rate on their own experience. Certainly if an expert other than an attorney is in court that a fact was a "usual" fact, the court in a Daubert-style motion hearing would demand something more than the expert's limited experience that the fact is "usual. "That should alert you --- will the attorney fee expert in court provide an empirical basis for his/her conclusion of the "usual hourly fee" that will stand scrutiny?
In short, your depositions of the adverse expert should explore the data the expert will offer to support his/her conclusion of "usual" hourly rate. A Daubert-style challenge may be possible to keep out the opinion.
Have you read What American's Lawyers Earn, in the March 2011 issues of the ABA Journal? You may want to use the facts about the yearly amounts lawyers earn (accessible through that article as a gateway) in your cross-exam of the adverse fee witness.
In talking with your own attorney fee expert, do you and your own expert know that rofessor Henderson's study "What American's Lawyers Earn", used in that ABA article, is built on limited US government BLS statistics and that Henderson's report has limitations (e. g., does not include what equity partners earn - and he omits the existence of several law schools in various cities). This report states what lawyers earn in various markets, not what they charge per hour. But an expert should be prepared to say he/she knows that the BLS has statistics on lawyer incomes, and why/why not they are applicable for use in your case.
There are many sources reporting what lawyers charge or what they earn, and an expert on attorney fees should have read several of them (not necessarily all of them). Familiarity with such sources adds depth to an expert's understanding of the market rate hourly fee for attorneys with the requisite skill in the jurisdiction involved.