I guess, this difference of the costs are not so important.
When the engine serves the purpose to produce a good selling product, I wouldn't care whether it costs one thousand Euro more or less.
In this case it is more important whether it offers a reliable and fast workflow.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt