title: Customizing default y-axis label in Highcharts
body: <p>I want to prefix a $ to the default y-axis label.  My bar chart is using values in the millions so the chart is returning value-MM (80MM, 30MM).  What I would like to do is format the y-axis like $-value-MM ($80MMm $30MM).  I have tried the code below and can't get it to work?</p>
  
  <pre><code>yAxis: [{ // Primary yAxis
      labels: {
          formatter: function () {
              return '$' + this.value;
          }
      },
      title: {
          text: 'Revenue',
  </code></pre>