I ran into this exact problem when getting bids for a small house last year. Right in the middle of my research, I realized that quoting 3D architectural renders works just like paying for printing 3d models on a site such as Gambody complex files with fine detail take more time and skill than simple ones. For a residential project in the USA, the final cost depends mostly on how much custom furniture needs modeling, whether you need day and night versions of the same view, and how many revision rounds the studio includes before charging extra. Some studios price per final image, others offer a flat package for a set of views. To estimate a reasonable budget before you call anyone, write down three things number of views, level of interior detail, and how many change cycles you expect. Then ask two different studios for a fixed price on that exact scope.