A few weeks ago, I picked up a healthy bunch of lemon basil at the farmer's market. I paid $1. When I got home, I used some of it in cooking, and stuck the rest in a cup of water. After 2 or 3 weeks, all the sprigs rooted, and I transplated them to my herb garden. I now have 5 healthy basil plants in my garden, for a dollar.
At a garden nursery I have paid as much as $2.00 per plant. I have also not seen the kind of exotic basil at nurseries that I see at the farmer's market, so I may buy bunch of purple basil and some thai basil--just for variety--next time I'm at the farmer's market.
I also rooted some nice spearmint from a snipping off of my sister-in-law's plant.
Thought I would share this tip with fellow Chowhounds who also like to grow their own herbs.