The screen can turn on but you can't touch the screen, it seems your screen is okay but the digitizer can't work, isn't it?
So you can only replace the digitizer but not the whole screen, and it will not cost $50 so much. And the new replacement is about $15(accord to the [http://www.witrigs.com/oem-digitizer-replacement-parts-for-samsung-galaxy-ace-2-gt-i8160-black|digitizer for ACE 2], and i think they cost nearly the same ), plus pay for repair, you can get how much will cost.