"because they are the same lure" - I'm not sure you can say they are the same lure. GY started a revoloution when he came up with this simple design that catches fish. Lots of people tried to imitate this lure and some did, but some didn't. There is more to a lure than the overall shape. When GY's son decided to start his own lure brand, Kinami's, his dad gave him the mold, but not the formula. There is a guy in this part of the country that manufactures a Senko "knock off" that works great and was used to catch the Kansas Small Mouth record a couple of years back. They sell for a lot less, and catch fish like crazy, but they ain't Senkos. What you have to consider is, do the fish know the difference? If they do, they may bite one bait when they won't bite another. Last year I fished with a guy using Kinami's in red shad while I used Trick Sticks in the same color. He caught fish and I didn't. Was it the bait?
GY is carrying all that money to the bank 'cause he has a product that people want. If they stop wanting it, you can bet your bottom $ that he will find another way to get that money, if he can.