[woolion]

It's still very hard to grow with high failure rates, but you can definitely find plants for affordable prices -- a bit less than 10$, but then you need to manage to keep it alive for 3 years if you want to enjoy it propagate it. There are a number of good YT videos on how to cultivate it, and some documentaries on professional plantations.

To have it the spiciest you should wait a good ten minutes or more, the spiciness is activated by the process: "The chemical in wasabi that provides for its initial pungency is the volatile compound allyl isothiocyanate, which is produced by hydrolysis of allyl glucosinolate [...]; the hydrolysis reaction is catalyzed by myrosinase and occurs when the enzyme is released on cell rupture caused by grating" (adapted from wikipedia)