Anything with a large backend is likely an intensive game, and aren't those cores written in native C/C++ anyway?.
Someone please take an app in Objective C, convert it to JS with route 66, convert to Java with (?) And convert back to Obj C with this tool, and share.
Where on earth did you get that number?
UI code in a well-structured application is a thin-shim on composed, testable backend code. It should be the least of the code, by far.