Economics Behind the Insulin Shortage?
You are missing patents. 

I recommend reading the paper "Why Is There No Generic Insulin? Historical Origins
of a Modern Problem" by doctors Greene and Riggs.


  ...high costs of
  pharmaceutical research and development are
  often invoked to justify the high price tags of new
  medications. Although the price point of effective new drugs — from hepatitis cures to new
  agents for heart failure — may initially be out of
  reach for many patients, market laws predict
  that drugs with strong demand should become
  more accessible after market exclusivity ends
  and generic competition begins. Since 1984,
  when the Drug Price Competition and Patent
  Term Restoration Act was passed, pharmaceutical innovation and access have been balanced on
  that premise: innovative drugs are rewarded
  with high prices during their window of patent
  protection, and generic competition reduces
  prices thereafter.
  
  [...] incremental innovation has repeatedly precluded the formation of a generic insulin industry in North America when earlier
  patents expired. The history of insulin hasn’t followed the standard chronology of pharmaceutical innovation, in which patent monopolies predictably give way to generic competition.
  
  Viewed in historical perspective, insulin is not
  a single entity but a family of related products
  that has evolved through incremental improvements. Subsequent iterations of insulin represented actual innovations, each one being safer,
  more effective, or more convenient than its predecessor. And yet after generations of incremental
  innovation, insulin may be no more affordable
  than it was when the original patent holders
  sold their stake for $1 to ensure access to this
  essential medicine. 
  Pharmaceutical-industry analysts have described a repatenting tactic called evergreening,
  in which a series of related patents — often on
  metabolites or optical isomers — extend the life
  of a product after initial patent expiration.