'You don't talk about money', this principle is quite persistent in some areas, but the approach does not lead to any change. Especially when salary discussions, new contract negotiations or fees are discussed, it makes sense to know which salary ranges are common in the respective area.
It is advisable that you take notes on why you earn more salary. These can be, for example, successes achieved, such as new orders, or similar. Further training that you have done is a good argument for more money. If you want more money for your work, you have to communicate.