Formatar valor chart PrimeFaces

Encontrei a solução,

Trecho da documentação:

3.15.15 Extender

Chart API provide high level access to commonly used jqplot options however there are many more
customization options available in jqplot. Extender feature provide access to low level apis to do
advanced customization by enhancing the configuration object, here is an example to increase
shadow depth of the line series where model’s extender property is set to “ext”.

<p:chart type="line" model="#{bean.model}" />

function ext() {
   //this = chart widget instance
   //this.cfg = options
   this.cfg.seriesDefaults = {
      shadowDepth: 5
   };
}

Refer to jqPlot docs for available options.

A partir dessa informação fiz o seguinte:

No Java:

barModel = new BarChartModel(); 
barModel.setExtender("ajustarGrafico");

Axis yAxis = barModel.getAxis(AxisType.Y);
yAxis.setTickFormat("R$ %'.2f");

No Javascript:

function ajustarGrafico() {
	$.jqplot.sprintf.thousandsSeparator = '.';
	$.jqplot.sprintf.decimalMark = ',';	
}

Agora ficou no formato que estava precisando.