They're not the same thing?
Why is Jam so much cheaper?
There were 14 voters.
So, basically five people don't know the difference, five people perfer jam, three prefer jelly, and one of the 14 ONLY wants to know why Jam is cheaper and apparently has no preference or doesn't eat it at all. Interesting.
I've been informed by three sources that the difference between jam and jelly is that jam is made from the entire fruit, and jelly is made from only the juice of the fruit. I suppose the juice extraction step is extra and therefore, more costly. You know, as opposed to chunking a bunch of whole grapes, strawberries, etc in big jam-making machine. Apparently I'm not the only person to consider this mystery of sticky fruit-based things. Please refer to this link for a concise look at the difference between jelly, jam, and yet another...preserves. If you notice in the URL, it's question 84. That's pretty high priority, if you ask me.
I now consider myself enlightened in the realm of sticky breakfast accoutraments. Except syrup. And don't even get me started on that.