I lived for about three years in the late 80s on $400 a month ($709 a month in today's dollars), sharing a place with my girlfriend/wife who earned about the same. Of course, this was in Montreal, so health care was not an issue, rents were low at the time, and I was a musician so there was no entertainment budget because I was the entertainment. After that, we had kids and lived on one minimum-wage salary and later student aid -- about $1200 a month, $1760 in today's dollars, for two adults and two young children. It was tough, but do-able.
My current projections are that I can retire fairly comfortably in Toronto on between $900 and $1200 a month (my share of rent or the fees/taxes on a paid-off condo, food from mostly Asian supermarkets and restaurants, lots of biking and transit, long-distance vacation every couple of years), although I won't have to.