1985 Honda Civic needs ball joint. Whats it worth?

You don't have to do ball joints together, you can just do the one that is bad. Check other sites for car value, such as: http://www.edmunds.com/ , http://www.hagerty.com/ (valuation tools), http://www.hemmings.com/ (i know it's not a classic, but it is getting old enough and people collect anything), http://www.nadaguides.com/ , also check the "sold" listings on Ebay for price comparisons and don't forget Craigslist. Even a running & driving beater is worth something, as it beats walking. Ball joints however aren't really an item you debate repairing in consideration of the value of the car, as it is a safety item. If the car is NOT worth the cost of the repairs, then scrap it or sell it for parts.