Why can a simple question cost a lot of tokens?

A simple question of a few words will cost only several or tens of tokens.

After accepting the question, AI will start processing with creating a context window which contains the question, retrieved data from inside or outside, and the answer, so that will cost a bunch of tokens.

And, when AI is answering, the data and the answer will be repeatedly processed what continuously cost a lot of tokens.

So, as the tokens will probably cost some money, how to ask a question and specify a range of data are very important to save money.