From what I can see now, I need to purchase Commercial edition (I wonder where could I get these 150 EUR... ) to make an actual 4-color game.

For such little game, 150 euros perhaps not !
There are lot of free engine like Ogre 3D , Irrlicht , XNA Framework etc ...
Perhaps not that complicated to such simple but great game.
For free you'll have shaders and all next gen stuff.

Your game would fit great in Iphone and mobile platforms !