Uter, Hippy or Jesse?
Jesse Grass can do all the recycling and railyard tasks with 50% extra materials. He also has a funny visual task at Krustyburger (granted its only for the 60 minute one).
Forum Discussion
If the character you're looking to purchase is mainly for the monorail then Jesse is definitely the best choice as he earns double the amount as the others although slightly over priced as you mentioned but the way that EA have been giving away donuts recently it won't take long to recover those extra 10 or 20 donuts in all honesty.
