I agree with other posters, 60% is a pretty good rate for businesses to succeed. I develop some as a hobby developer and two of my apps - Toy Cash Register -- and Kids Writing Pad have made over $6,000 each -- I develop myself and sometimes outsource design (which could use a lot of improvement) -- as for marketing, it's a waste of money. You need to find the right company to provide the right marketing, and to be honest-- it doesn't exist. There are companies to mass market, but you aren't going to win in the mass market -- it took Rovio years to get a success like Angry Birds--and in the niche markets there isn't enough experts--you need to make it your own way and not lose money on people trying to market you. I wrote apps because I needed them-- and it pays for my Apple device addiction.