If you don't smoke, why on earth would you need matches? Well, if you're going to learn to cook like granny, that will probably include cooking on top of a wood heat stove or on a wood cook stove with an oven. I know there are ways to start a fire with a magnifying glass, some straw and some kindling, but believe me, matches are easier.
If you're really good at starting and keeping a fire throughout the three daily meals, you could use as little as one match a day. If you're not, 20 may not be enough. We have found that the most economical matches are book matches, like you get with a pack of cigarettes. They come in a box of 50 books, 20 matches per book, for about $1.50 in many stores. That's a lot of lights for cheap. Wooden kitchen matches go for about $3.50 for 250 matches. See the difference? When you're living off the grid, every penny counts.