What's the best grade to buy for a given coin? The answer is not one size fits all, unfortunately.
For example, take the 1935 Old Spanish Trail commemorative half dollar. It has a small mintage of 10,008 pieces and it’s an expensive coin in all grades. However, when one considers that a relatively unattractive example costs nearly $1,000, a Mint State 64 representative at the $1,200 level seems reasonable.
At a 2013 auction, one graded Numismatic Guaranty Corp. Uncirculated Details, Improperly Cleaned, brought $940. That same week, two handsome MS-64 examples sold at auction for $1,116.25. The difference between a so-so coin that may be hard to sell and a nice coin seems relatively modest in this case.
The jump to MS-66 is, again, rather small, with attractive examples selling at auction at the $1,450 level and oddly toned ones selling cheaply at the $1,200 level.
This commemorative provides a useful case study on when it makes sense to pay a little extra for something nicer, especially when buying an issue that is inherently expensive due to a low mintage.