I believe deficiency is the precursor to a plethora of diseases and cancers. There is quite a bit of literature on the current impact of deficiency - you will find it implicating everything from poor dental health to the surging autoimmunity rates in the US.
In terms of the financial impact of deficiency, I found this fact on
examine.com very interesting:
In general, supplementation of 1,000 IU vitamin D3 daily (seen as a lower dose estimate) has been estimated to reduce the medical costs of cancer treatment by about $16-$25 billion by exerting a general protective and preventative effect.[78]Also, the cholesterol hormone is a
precursor to vitamin D, so the current low-fat (and low cholesterol) dietary recommendations are only contributing to the problem.
Best.