I am not sure of the going rate with you, but what I did was trawl a few markets, estimate a price from what was on sale there and then make sure this covered my costs. The price I arrived at has never been quailed at. I charge exactly the same for everything, finding I make a good mark up on things like lemon curd and almost nothing on others. Again no-one has complained. Lastly, when I costed out some jams, like my absolute fav Melon and ginger, I nearly passed out and decided not to offer this for sale.

ps; my price is 5 euros per 340g jar

just be careful on mailing jams; they are really quite heavy and I found the cost of postage almost as much as the cost of the jar...