Instead of paying nursery prices for these staples, even if a little cheaper at you favorite volume hardware joint, consider growing on the supermarket varieties. That's right, if the roots are intact, you can replant the Basil and Spring Onions. You can do it with Coriander too, but I have had less success with that.
A little wise shopping at the Central Market or your local supermarket will yield Basil with its roots intact for between $2.99 and $3.99 and a bunch of Spring Onions you will find for as cheap as .99c or $1.99.
With the Basil, it often comes with a plastic wrapper, so what I do is discard the wrapper and place about 100mls of water in the bottom of a tall glass. Place the Basil in the glass, and keep on a nearby windowsill in the kitchen, where there is a little sunshine and maybe a breeze. I have kept one plant producing fresh leaves for up to 3 weeks. With a bit more diligence than I have, I am sure you will get even better results. Replace the water every couple of days, and make sure it never dries out.
Spring Onions are an even more exciting story. As long as the roots are attached, the onions will continue to grow in the ground. So if you can, try to get the large bunches of small plants, often available in Asian supermarkets for not much money. You can plant two or three groups of clusters in different parts of the garden, and then pick just one or two plants as you need them.
Ironically with Coriander, I have found the opposite strategy applies. The last visit to my local giant hardware store yielded a mature 16cm pot of Coriander for not very much; I think I paid $12.99. Well, rather than paying for picked Coriander at the supermarket, this little pot of Coriander has been regularly harvested for a curry or salad and after 8 weeks in a shady spot, and regular watering, it continues to thrive.
So for Basil and Spring onions at least, you can stop wasting what you don't need. If you are anything like me, these are a small but deeply fulfilling triumphs.