Our total cost for the system to develop was about $80k, monthly running costs for this software project are ~$1900/mo. Everything is run "in house" (dev servers onsite, colocate everything else) but using openstack/heat we can deploy a hybrid solution using aws/rack space/vmware with a few clicks. Comparative SaaS solutions come out to near $4000/mo.
I'm working on my own app right now. The total cost depends on many factors. That's why I prefer to hire software product development team from clockwise.software. They provide all development services from the discovery phase to the app’s launch and continuous updates. Hope with their help I'll finish my app at the highest level and at competitive price.