AdButler
Pick it if: you want to know the price up front, launch in days and get real help, across web, app and newsletter inventory.
AdButler is a hosted ad server with published monthly plans, a white-label portal for advertisers and support that includes help moving off your old system. It can serve display, native, video, in-app, sponsored listings and email newsletter ads from one account.
Cost: Published plans from $179/month for 1M ad requests.