As an MBA, I will tell you that how much something "costs" depends on how much you pay for it. If you pay $1 million, that's what it cost you. If someone else can buy the same thing for $10,000, that's what it cost them.
There are many factors that influence the cost of a trial. Yodon has listed some of them.
You can find a "full service" CRO that will take care of everything from regulatory authorizations to study design, protocol/consent/CRF development, to budget negotiations with the investigators, to monitoring, to managing study supplies, to data management, to final report. They typically work on a basis of 1/3 cost, 1/3 overhead, 1/3 profit, so anything you can competently handle yourself can reduce your costs a good bit. CROs are usually willing to give cost estimates, but the reliability of their estimate depends on the information you are able to provide them. You will get the best estimate if you have a trial protocol available for them to base their estimate on.