It depends on how fast you want one, what model Jeep it is for, and how far you are willing to go get it. I have found tops from $150 and up. And the doors are pretty much the same. That is for a CJ7/YJ top and doors.
I bought my top and doors thru an Ebay auction and wound up spending $2550 but the guy who had them was >100 miles away so shipping was a wash I just went and picked them up, Turns out they had never been used. The guy bought a 2000 model and took doors and top off and stored them so they were like brand new.