If you like Asian food, chances are you have at one point or other eaten a product that has been identified as "wasabi."
I can tell you without a doubt that what you had is not Wasabi but rather a mixture of common Western horseradish, mustard powder and green food coloring.
True wasabi is rare in the United States and when you find it it is extraordinarily expensive.
If you want to try growing it I've seen seedlings for sale on the internet for $17 each and small plants for $29 each.
There are a couple reasons for the high price. First the plant is very picky about growing conditions. If you are not on top of it, the plant will most likely not survive. It needs daily care with misting and precise temperature, lighting and humidity.
If you do get it to survive and harvest the rhizome, you have to be careful with how you store it.
And once you put it on your food the essential oils dissipate within about 5 minutes so eat quickly.
If you want to try the real thing you might be able to get it in an Asian restaurant or specialty store. Just remember if the price is good it's probably not the real thing.