Appraisal for items with strong secondary market...

Wondering if I need an appraisal for the following situation.  I have an 1878 Morgan Silver Dollar that I bought 20 years ago for $500.  It is now worth $15,500.  It is professionally graded by PCGS as an MS65, and there is a strong secondary market with a ton of activity.  Do I need to pay an appraiser $1000 to simply look up the price online?  Or is the vast secondary market and professional grading enough so that I can deduct once I donate?  The appraiser would not be allowed to crack open the casing of the graded item, and would just go off the details with a simple online lookup.  It seems as if the grading company, like NCG or PCGS, would be the appraiser of record, although they don't assign a value to the items due to the nature of the secondary market.