not enough
This seems to be a jpeg of the subway map that you can see on the wall in every train station in Shenzhen and aside from zoom capabilities offers nothing else. There could be exit guides, click on a station to see what attractions or shopping are near that station, even a photo or two. As such, I think it should have been free.
SpikeHK about
深圳香港地铁指南 Shenzhen Hong Kong Metro Guide