Ok so here's my tip: How to easily double your expensive jam
I've only done this with the 'simply fruit' type of jam not jelly so I'm not sure how it would work but anyway when you have an empty jar of jam, save it. Then when you buy jam again take half out, add some water (i buy the small jars so i only add about 1/4-1/3 cup water per half), then heat thru in the microwave until just hot. Pour back into the jar and refrigerate. That's it. It gels back up and will be firm just like before. If your unsure then just start out with less water, but anyway it's a great way to make your jam last longer, definitely worth it for us!