Debra - I'll guess that your client is a lender. They often use the term "jumbo" to identify a loan of more than $250,000 so they likely carry that term over, thinking that it fits the appraisal terminology too.
Some states impose certain limitations related to "transaction" value on appraisals that a licensed residential appraiser may perform. Typically a licensed appraiser is limited to appraising residential (1 - 4 unit) properties in which the "transaction" value is under $250K - above that requires a certified residential appraiser. It falls under the heading of scope of practice but since no one can agree on the definition of a "complex" property, it's pretty uninforcable.
Like Larry said, quote 'em a fee based on the amount of time you think it will take you to do a credible appraisal - not on the appraised value (contingent fee). Usually I tell 'em my fee is $50 per door nob.
One very important thing to consider in your fee that Larry or Doug did not include is your liability exposure. Because the loan amount and the value are going to be higher than usual so is your liability. If you get it wrong and are sued your potential loss is greater. I am sure your insurance company would advise you to do a very thorough job and subsequently you would need to charge more.
The lender is no doubt making a jumbo loan. If the property is in a neighborhood of similar properties and data is avaliable perhaps it should cause you no problem however if data will be hard to find or the property will be difficult to inspect you should charge more for the job.