Because venues are expensive. Conferences have always been expensive.
Google IO used to be $900. I believe the prices are more expensive now. I haven't been since 2017.
Discussion
Next week I'm going to London, UK, attenting a 2 day convention (it's an ERP solution). Full Price £150.--, 2 hot buffet lunch included. The price amount will be credited on my account wallet to spend on extras.
5 years ago, I went to another 2 day convention (document management company), in Berlin, DE, full price €120, with buffet lunch, and evening restaurant.
Prices have dropped quite a bit for me!
Every year I attend a conference of the ERP we use for work, I can safely say that it is useless. This last year I sent some colleagues on my behalf, I feel like I'm wasting my time there.
I suppose they have their usefulness, but I have always felt there in the middle out of place, in this sense I am with Semisol, if I think about it carefully it is all pure marketing. All the companies that attend want to sell something or themselves.
It's like a shopping mall, I never saw the point, walking around to see which store gets your attention so you buy.