You’d Know If You Had Real Wasabi
Not only is real Wasabi incredibly expensive, but it is also hard to grow. Chances are, what you’ve had is horseradish, paired with pickled ginger and perhaps (a drop of wasabi), with your sushi. Is your mind blown?
The real deal wasabi is just not hard to grow, and expensive, but it is not practical for restaurants to keep in stock. The ingredient is most ideal when eaten within 15 minutes of being grated. It does not have great shelf-life, when you put it that way, making it less viable to keep in stock. Guess you will have to settle for more horseradish with green dye in it.