On medical student selection, the process is more than marks, but marks still count a lot, because there are presently over 10,000 qualified medical applications for approximately 2,500 intake positions. The universities have no option but to put in filters to whittle down the pool of people they're going to interview and test further. Whether they are grade-point averages or scores on the MCAT, marks are unfortunately the easiest tools at hand.
Your point about their personality types is interesting and important. Many schools have a very individual approach to the medical students they like to think they take, and therefore the product they would like to have, but they don't apply those tools except in a more general interview. We're not making the best use of psychological testing of the applicant pool to try to sort out at least those who have a high likelihood of failing to show the personal characteristics that are important.
You asked about the average cost to train international medical graduates. This is highly dependent on where they were trained and in what practice. It differs from specialty versus primary care. Many provinces have special programs to monitor and mentor these practitioners to get them into practice situations to see if they can be licensed. Other international medical graduates--and I remind you that these are all landed immigrant Canadians--are not ready for practice and are waiting for residency training positions to get licences. Approximately 300 positions are reserved in the residency match at the first-year level for these individuals each year.