Everyone has different levels for what "expensive" means. You can get new HDMI monitors for well under $150, and new DVI monitors for well under $100, and DVI<->HDMI adaptors are under $10.
Whether "it's expensive" depends entirely on the market. There are markets (developing countries, education) where tripling the total cost of the setup, compared to using a monitor you already have, is significant.
Everyone has different levels for what "expensive" means. You can get new HDMI monitors for well under $150, and new DVI monitors for well under $100, and DVI<->HDMI adaptors are under $10.