A valuation of $6,462.50 for a 1976-D Bicentennial Quarter in regular clad (non-proof) condition seems exceptionally high and potentially erroneous.
While the Bicentennial Quarter holds historical significance and can have some collectible value, such a price would be unusual for a circulated, non-error coin.
Regular circulated Bicentennial Quarters from 1976 are typically worth face value or slightly above, especially in circulated condition.
f this valuation is referring to a specific error or variety of the 1976-D Bicentennial Quarter, such as a double die or other rare issue, then the value could indeed be significantly higher.
However, it's crucial to authenticate and verify the specifics of the coin before accepting such a valuation.
If you're considering buying or selling a 1976-D Bicentennial Quarter, I would recommend consulting with a reputable coin dealer or professional grading service to get an accurate assessment of its value based on its condition and any unique attributes it may possess.