On: Q: “How much does an app cost?” A: “About as much ...

[whatusername]

System/360 (if you can count it as an app) was supposed to be $5 billion in the 1960's. So $34B + in todays dollars. http://www.wired.com/science/discoveries/news/2008/04/dayint...

(And if you include the cost of further development of z/OS over the years that goes much much higher again)

[rhizome → whatusername]

I wouldn't be surprised if that was one of the priciest projects with the best ROI, though.

[whatusername → rhizome]

Actually, thinking in terms of largest total return for a project (ROI is infinite if your I is 0).. I can't think of too many projects that have had larger returns.

Probably the iPhone? Maybe some Cars (camry? Model T?) Maybe some really big mining/oil operations? What else is in the same league?

[rhizome → whatusername]

To be sure, there has been marginal investment over the years in maintaining absolute backward compatibility through the zSeries/zOS.