re: What is a good price for basil? What about thai basil?

No, basil doesn't last forever. It lasts until it flowers & goes to seed, then it dies. And basil will flower as soon as it has eight pairs of leaves. To prevent it from flowering, you need to pinch back the developing flower bracts--this will cause it to grow bushier instead of flowering.

It will also surrender to cooler weather; it browns & quits looking decent in the high 40s. So it won't survive even a south LA winter, unless it's in a very warm/protected area or brought indoors or grown under a cold frame. High heat, on the other hand, doesn't bother it. It likes to be moist, but not soggy. Too dry is not good (unlike thyme and sage, which prefer to be on the dry side).

If you keep it pinched back all summer, you can let it go to seed in the late fall when temps cool off. Allow it to set seed, let the plants brown up completely, then strip off the seeds and scatter wherever you want basil. Come spring, you'll get a nice crop of self-seeded, second generation plants.