Adding currency prefix to AmCharts

To add a prefix to value axis:

valueAxis.unit = "$";
valueAxis.unitPosition = "left";

In case you need this in a balloon, add it to balloonText:

graph.balloonText = "$[[value]]";

For AmCharts v4 you can add a dollar sign using this:

chart.numberFormatter.numberFormat = '$#,###';

https://www.amcharts.com/docs/v4/concepts/formatters/formatting-numbers/