There are now many tech blogs, YouTube channels, and websites dedicated to posting about tech, so people can learn about tech on tech blogs for free and at home on their computer. Stores like Bestbuy can also be used to show off new tech.
I think if running an electronics show become too expensive to host, electronics shows will be gone. The company which run the electronics show may not be able to afford to hire many security guards, cleaning staff, construction workers to build the stages, and other workers to keep visitors safe, and comfortable if they can't sell enough tickets to an electronics shows, or can't find enough sponsors to help pay for the expenses like workers, rent, electricity, etc.