For the jams, I would prefer to sell them in smaller 6 ounces jars because I don't want to charge too much by jar. (My batches are small, I only use the best local, organic, seasonal fruit, and I spend a lot of time on them.) However I am limited by the type of jars I can find easily and at a reasonable cost. So far the best option for me has been 8 oz mason jars that I can get for about $8 for a dozen.
I have to calculate my costs, although I am obviously not doing this to make money (it's more like a fun thing to educate myself and my daughter about what it's like to make & sell things that you make). It's more to make sure that I recover most of it! 
