feeling disappointed just got to contract 60 with Ethan to find out it needs a total of 28 000 000 materials for a reward of 345 000 of experience and a space theme
Look on the bright side. You don't have to do any more Ethan contracts and you are probably enjoying some of the stuff that dropped along the way like buildings and gems.
Meanwhile...consider investigating the contractors in the TS Wiki. They tell you what all the contracts and rewards are for each contractor. Then you can decide in an informed fashion about what contracts you want to pursue.
A place to start: http://trainstation.wikia.com/wiki/Special:Search?search=Contracts&fulltext=Search&ns0=1&ns14=1#