From working at a
raw food restaurant I thought about this question a lot too because we were always soaking nuts and seeds, often until they sprouted.
The quinoa is definitely worth experimenting with. Seeds of change lil packets are 2.69 each, whereas bulk quinoa from a store is way cheaper. If they can sprout little tails they can be plants, I say.
Like Dave says, for seed saving it may be worth it to know what variety you're starting out with. BUT personally I err on the side of cheaper until I get myself organized
enough to successfully have plenty to eat and more to save.
Right now I've got potatoes, sunchokes, and garlic in the ground that are all from the produce counter. I thought about buying seed potatoes, but the high cost when they're going into a new garden of mine is too much. Especially when the soil might suck for potatoes, etc.
My philosophy: make plenty of mistakes with the stuff at hand. Then, when I know what I'm doing, the investment for fancy varieties will be worth it.