Sold by the approximate gram weight of each seed.
[Given the wide variety of these seeds in terms of size and weight, we've reconfigured our pricing to work out a little more fairly. Note that some seeds are larger but weigh less than smaller ones. You can get an idea of the variations by checking out the "group photo" on this listing.]
The meat of the seed has traditionally been used to aid in lucid dreaming, and has also traditionally been used as a topical remedy for toothaches, muscular/skeletal discomfort, and even jaundice and ulcers.
The seeds very hard-wearing with shells so tough that they can float along in seawater for months and still result in a plant when they make it to land.
As such, they make excellent good luck charms and talismans believed to bestow protection and aid in communications with the spirit world. (They also just look cool.)
They can also be planted, though if it gets cold outside in your region, you'll need to keep it inside. You can use a basis of compost with a layer of soil on top in a tall pot. Drill a hole in four points of the narrow edge of the seed, (like N, S, E, W) and push it into the compost, cover with soil. It's very fast-growing and has tendrils that will latch onto whatever is near, so it works really well with trellis planters.
For lucid dreaming, those using the seeds have merely consumed the white meat inside, starting with a small amount to test tolerance and ensure there are no allergies, then increasing the amount they eat, or they would chop up and grind the meat of the seed, powder it and add it to tobacco to smoke.
To wear as a talisman, scratch a starter hole with an awl or a nail, then hold the seed in a vice and drill a hole near the side you determine should be the top. There is no need to coat it or treat it, but you can coat the inside of the hole if you wish, to prevent decay. Put it on a string or chain of your choice. It's common practice for those seeking its magickal properties to thank the spirits of the plant for the gift.