ruby code  case when not so dry
You can try:

day = case self.type
  when 'fast'       then :fast_completion_day
  when 'super_fast' then :super_fast_completion_day
  when 'ludicrous'  then :ludicrous_completion_day
  else                   :budget_completion_day
end

self.value = Increment.first.max_hours * Incrementor.first.send(day)


From a friend that knows more than me:

prefix = %w[ fast super_fast ludicrous ].include?(self.type) ? self.type : "budget"
self.value = Increment.first.max_hours * Incrementor.first.send(:"#{prefix}_completion_day")


This is probably about as short and dry as you can get it. That said, I'm not sure that this is more clear/easy to read. I'd probably add a method to Incrementor like Incrementor#completion_day_for(type) that would take care of this logic for you.