Well from what i see, i feel like people use tenergy just becauses its expensive and because the pros use it. Being a MX-P user, i feel like this rubber is the same as tenergy, but at a lower price. Tenergy for be is good, but the price is just not worth it. Since many think its the best, pros use tenergy as they are most likely sponsored, causing them to get them for free.
It's no use blaming the money for the sake of the pros.. If you are at that level, you want to use what works best for you, and if that rubbers name is Tenergy05, you use that rubber, regardless of what brand's sponsoring you, because being a pro, you have the access to any rubber out there if you just call that guy and know the secret handshake he uses.
For mid-level players and lower, you may be right that it's okay to play with a substitute for what you would normally use because it's cheaper.. But for them top pros, they play what is best for them, if the rubber's called Airoc, Tenergy, MX-P, Rasant og Hurricane - it doesn't matter
The thing about the Tenergy, it's got that special feel that no rubber has, and it lasts long, and it's also stabile when it comes to performance. Many other rubbers ain't that stabile, the rubber reacts different to the same impact on the same ball, but the Tenergy does this less than other rubbers. Meaning you can really rely on this rubber. Ofc other rubbers have this characteristics to, but in different forms. So again, the pros don't use this rubber because they are sponsored, they use it because it is the best. Hobby players and even som rocket engineering forum members miight use it because of the money and reputation, but yeah..
Hope you got my point and I didn't offend you, I wouldn't like to get chased by the infamous goon squad this time a day