One of the indie industry perennial questions is: how much money can I expect to make? Less asked is: how much money can I expect to spend? Your pro forma will need both rows.
Most projections will only factor in the cost of production, and do so erroneously. This is because most “indie developers” haven’t a clue as to what game development costs. But beyond production projections, and unless you’re relying solely on grassroots (social media) efforts, you need to factor in marketing. How much does it cost to make money? Artyom Dogtiev gives us an idea of CPI (Cost Per Install) in the following article:
http://appindex.com/blog/app-monetization/much-cost-get-app-install/
I found some of the numbers quite shocking! What about you? Let me know in the comments what you think.