You are right. The carports are not cheap. However, I am chronically ill and we needed to re-do our chicken pen to make things easy for me so I could continue to keep chickens and be able to care for them by myself. For security reasons and for my ease of use we knew we needed a covered run.
My husband ran some numbers and the amount it would have cost to build a covered wooden run this size was close to the same as purchasing a carport. Plus there is my husband's time, paint and roofing on top of the lumber and HWC costs. He works 6 days a week and it would have been months and months until he got a run built. So he decided a metal carport was money well spent and it was installed as part of the price. We did have to pay extra for a snow load roof, but this should last us the rest of our lives.
We placed our run directly behind the fence at the end of our driveway. Should we ever decide not to keep chickens anymore, the fence and coop can be removed and the run used as a carport. I tried to plan ahead just in case and for re-sale. Works for us!