I came across a canning process that actually reuses glass jars! :) Our grandmothers used to use parafin wax to make sure they were sealed properly before putting the lids back on. Parafin wax costs about $8 for a 1 pound block. You should know that the FDA discourages this method in favor of using 2 piece lids on mason jars, to ensure a tight seal. This method, however, is cost effective and encourages self-reliance, and actually works if you do it properly. So if you're up for the challenge, take a look at this youtube video for simple instructions on how to do it!
https://www.youtube.com/watch?v=qSkOnmGcgAw
https://www.youtube.com/watch?v=qSkOnmGcgAw