Still well short of the at least 3,000,000 or so Canadians this would represent 

At even 1,000 separate diseases (highly unlikely) that is still 3,000 cases

To say nothing about the severity of each (a disease/condition may be rare, yet hardly noticeable as it relates to living a normal life)...

Totally agree though, a cost benefit always creeps in. I have a friend whose stepson had an exceptionally rare genetic disorder - I think he once said there are but 50 cases in North America. As such, there is little research, treatment, etc..