Ah, yes, you also need to split out between basis and growth.
No, it's not simple - and be sure to charge for your analysis time. However, if you can get the client $2,500 in tax credits that lowers his overall tax hit by (guess the amount; I've seen $300 extra income tax to get that $2,500 credit, plus a couple hundred extra for your time) - tell the client he spent $500 to get $2,500; $2,000 more IN his pocket. They like that.