The original goal was to tie produced clips to the money, by a function of time of certain types of frames on the clip (e.g. more usable film time on a clip = more money) making the player need to cut good clips without a lot of blank time as the reel spools faster and faster. Really this would only take a half hour to have added but I didn't have the time to finish it today.
As a placeholder, score is calculated simply as a multiple of the number of frames of the latest clip. So I guess really the only difficulty is clipping as big of a chunk as possible (one snip close to the end) before it runs out.