SimCity Build it

You may be looking at this in the wrong light.  Maybe I can help shine some light on the subject.

Looking at your image, you have 3 cameras and 9 cameras are needed,  The buttons says "18 sim cash".  If you click that 18 sim cash, what happens is you pay 18simcash for 1 camera.  So you would not see a check mark.  You would see 3 cameras turn to 4 cameras.  So to use simcash to complete the 9 cameras, that would be 18 simcash times 6 cameras needed totaling 108 simcash needed just to have enough cameras.

That is how it is supposed to work.