Your math seems to be wrong; and labor costs (now) in lower margin industries are more along the lines of 15-20% of gross revenue.

One employee working full time currently earns minimum wage of $11.40, or $23,712 per year.  Once the wage is bumped to $15/hour, that wage equals $31,200.  This means that each worker will cost approximately $7,500 more than they do today (keep in mind that this doesn’t include other additional employments costs; Ontario pension, etc.).

An employer has to generate additional revenue of at least $7,500 more per year per employee than they do now just to have the same revenue after cost of labor as it does today.  For a small business employing one person, if we use a 15% cost of labor illustration, that employer has to generate at least 3-4% more in sales revenue just to be in the same after-labor position as it is today.

This hypothetical company will have to raise prices by 3-4% and/or cut costs.  Smaller companies will be impacted most.