Just How Bad Was the WTI/Western Canadian Select Heavy Crude Oil Discount?

The Oil & Gas Journal is reporting:

The price of Western Canadian Select (WCS) heavy crude oil rose from $58.38/bbl (US) in February to $66.73/bbl in March and about $68/bbl in April, reported the analyst, Patricia Mohr, in a commodity price report.

The WCS discount against West Texas Intermediate crude fell from a record high $36.94/bbl in February to $26.23/bbl in March, $23.07/bbl in April, and, based on futures values, $13.90/bbl in May. The WCS discount is growing again in June.

It is my understanding that it is more expensive to produce oil in the Canadian oil sands compared to the Bakken. 

Everyone has their own numbers, but my numbers: Canadian oil sands need $60 oil to make money; the Bakken operators can make money on $40 oil. Some say those figures are high.