You might notice that 2500 years ago is a lot less than 5000 years ago. 5000 years ago, there were no guides to the pyramids. There was no tourism. There wasn't really writing, either.

Today tourism makes up a little more than 10% of the economy of Egypt. 2500 years ago, it would have been around 0%, for the simple reason that almost nobody could afford to be a tourist. The big businesses were grain and gold. 5000 years ago, it was actually 0%. That's when the desertification of the Sahara began and the people who had lived there came to Egypt and inserted themselves at the top of society.