In his blog Cornelius Schumacher wrote that is the size of the KDE core module is 4,273,291 lines. These numbers are generated by using SLOCCount. Next chart shows how are lines distributed in KDE core modules. 

He added that these four million lines are only KDE core and There are tons of applications which are not part of the standard KDE distribution.
"Concluding random data point: SLOCCount thinks that it costs $ 175,364,716 to develop the code of the KDE core modules. " Schumacher wrote.