IMO this isn't a great question...I'm sure there are companies out there with high volumes of production sales. However my guess is that those sales are going to people that aren't enthusiasts like many of us here, who are in the minority in that many people are non-knife people (varies by region but think that can be said as the general consensus).
If you are truly interested I would suggest researching each of the top companies individually and looking at their total revenue. Any google search seems to show more opinion based lists than factual ones, but I didn't search long before I replied here which is why I started off stating that this is my opinion. I'm sure there are some members here that could answer the question for you but a little research could probably yield the answers you are looking for in an unbiased way. Good luck my friend!