I just heard it on radio, but I am pretty sure that "on the average" is incorrect.
On the average, the prices for cars will increase by 2 494$ if the tariffs against auto imports is implemented.
This is a point of difference between English dialects. I think most dialects used for formal registers would not use the there, at least not in the formal register. However, if we are talking about an informal register, there are dialects where this is common. As tends to happen, this also means that, in some dialects, it is gradually becoming more acceptable in more formal registers.