that's like asking what the price of a new car is without specifying what car or what you need from it. It also depends what tooling you have available to you? If you have access to a lathe or a mill then you will be able to do most if not all of the construction yourself. Otherwise you will need to outsource it. Kenny is usually the go to guy for machining parts.

I have built spinner setups for less than 100 quid in the past but it all depends on what you're after.