When I tally herbs for this project, I tally only the herbs that I've dried and stored, thus replacing jars of organic herbs I would buy at the grocery. This year, I dried the equivalent of two jars of sage and one of thyme. The average price for organic herbs is $3.39 a jar, so I saved myself $10.17.
This is a bit inaccurate, however, because of all of the bounty that doesn't show up in the spreadsheet. I still have plenty of dried oregano, basil, and marjoram in the pantry from last year, so I've made no purchases there. And, of course, we had fresh basil (which does show up in the spreadsheet) and fresh dill (which does not) all summer. My sage plants will be healthy until a really deep freeze, so if I want more sage, it is right outside my door.
Overall, this is my best recommendation to gardeners with only a small strip of land: plant herbs. Sage will come up year after year to save you purchasing jars at the grocery, and basil is something you can hardly find fresh for retail purchase. If I ever have just a small strip to garden, I'll put in a couple of tomato plants, a basil plant, and a sage bush, and I'll still be saving money.
Tally through November:
3664.0 ounces harvested
229.0 pounds harvested
Total retail value: $773.84
Total saved: $469.96