It varies from costume to costume. It is highly depended on which tools and supplies you have access to, what parts you use, who you buy from, where in the world you live and so on.
It is for instance more expensive to make a costume in Norway than in the US, because more of the necessary parts will have to be imported, adding expensive shipping and import taxes into your final budget.
The costumes are highly detailed and as close to screen-accurate as you can get, so expect to pay anywhere from 5.000 to 100.000 NOK (≈ 500 EUR – 10.000 EUR).