What is the value of a 1873 half dollar?

This coin was minted in 7 different combinations of design and mint mark, so it's not possible to tell without pictures. Your best bet would be to either post a couple of scans on a site like CoinClub.com, or take it to a dealer for evaluation. Values can range from $25 to $6000, so it's important to find someone who is familiar with all of the possibilities.