In the rules thread says this:

• Trades that mean an unfair profit
  to the higher ranked player by falling outside the following range of
  ratios will be considered as Pushing cases:
  
  3:2:1 Where each unit of deuterium is worth 2 units of crystal or 3 units of metal.
  
  2:1:1 Where each unit of deuterium is worth 1 unit of crystal or 2 units of metal.
  
  

what its bothering me is:

2:1:1 Where each unit of deuterium is worth 1 unit of crystal
1 deuterium 1 unit cristal? never saw this ratio.