Yes, 5G phones are more expensive than 4G phones. But 5G isn't everything that affects the cost. Other features like cameras, display, battery, the design also matter when pricing a phone.
Companies are trying their best to keep the cost lower. In return for that, you would have to compromise on specs, like build quality, cameras, or processor.
There are a lot of inexpensive 5G phones in the market that have compromised the specs just for the sake of 5G.