Lysozyme is somewhat pricey, but you don't use very much of it. It lasts a long time. 50 g costs $35, but for a 6 gallon carboy, you use about 6 grams or $4.20 so that works out to about $0.15/bottle. And after adding that, it should be safe to add Potassium Sorbate, if you wanted to backsweeten a wine. I also believe that storage long-term isn't an issue.