Size isn’t everything but the larger wasabi is, the more expensive due to the fact that it takes longer to grow. But the average wasabi takes years to grow to maturity so when it comes to fresh wasabi, you need to pay or forget it.

The best known wasabi comes from Shizuoka and is $350+ per kilo and has nothing to do with the garbage that is sold in the west: https://mesubim.com/2014/03/17/wasabi-jpy-35-000/ but if you unlucky enough to eat Japanese food and taste powdered wasabi, run away from it’s chemical crap and not worthy of the tube or pot its sold in: https://mesubim.com/2012/12/18/green-poison-2/