Is hair transplantation very expensive?

Currently, I am losing a lot of hair and it looks unpleasant in many places, so I want to get a hair transplant. Hair transplants are quite expensive, but are the results worth it? I can't ignore the cost, so I want to do it but I'm hesitant. Also, there aren't many honest reviews about how effective the maintenance is, and there are many advertisements on the internet, making it hard to tell the difference.

If the treatment is ineffective, I wonder if it's different for each person, and if hair loss continues even after hair transplantation... I am concerned whether it's useless.