The finest known 1802 half dime is an example that has been graded PCGS AU-55. This is followed by one or more examples graded by NGC as AU-50. The NGC census shows three pieces graded as such, but this may be inflated by resubmissions of the same coin. There have been no pieces certified in uncirculated condition.
Below the AU level, VF-XF pieces remain extremely rare, possibly numbering less than 10. Below that, the concentration of coins are in AG to VG grades, often damaged, cleaned, or with other problems. These account for as much as two dozen pieces within the total known population. When this issue makes an appearance at auction, it is generally these lower grade and problem pieces that are offered.
The value of any 1802 half dime is difficult to determine because of infrequent offerings and the impact of the overall eye-appeal of the issue and the demand at the time of sale. This is true for most United States coins, but it seems to be on the more extreme end of the spectrum for this issue. One example graded by PCGS as XF-45 sold for $299,000 at an auction in 2006. This was followed three years later by the sale of a different coin carrying the same grade of PCGS XF-45, which sold for the significantly lower price of $195,500. While the first price was somewhat on the high end, the second price may have been a bargain, as a NGC AU-50 sold for $345,000 in 2008.
As for the lower end examples that are more frequently offered, prices are influenced by the nature of any problems as well as overall eye appeal. In the current market, any 1802 half dime regardless of condition tends to sell for at least $15,000 or more. Problem free coins which receive a numerical grade from PCGS or NGC can typically sell for up to $100,000 or more.
Extensive research by David Davis has showed that on average, over a 140 year period, only one 1802 half dime is offered for sale in any given year. This provides collectors with very few opportunities to acquire this famous American rarity.