I talked to these guys at the Chicago conference:
http://www.modulusglobal.com/They mention a ~$20K package would do the trick. What's everybody else's assessment?
IMO You will probably pay 20k for consulting alone.
My assessment is much more depressing:
Half a million from the top of my head. Million is more likely if you starting with money alone (no office, no hardware, no lawyers, nothing but bank account). This money will last you ~6-10 month of developement. After that you will end up with maintenance cost of another 500k/year.
That includes hiring full time professionals (programmers, admins, security professionals), building and maintaining infrastructure etc.