Today, trappers are paid by the government of Ontario to harvest the castor sacs of beavers and are paid from 10–40 dollars each when sold to the Northern Ontario Fur Trappers Association. (from wikipedia)
I also read something about people farming beavers for their fur, so I would guess that is the bigger part of the process.
If you want great vanilla taste then buy some good quality beans, split them down the middle, then soak them in a high quality vodka for a few months. As you use the extract you just need to top off the bottle for an endless supply.