Using Global Variable as Price for Variant
Removed the var_dump() from setting the variable as follows, and it works perfectly:

craft()-&gt;on('commerce_lineItems.onPopulateLineItem', function($event)
{
    $lineItem = $event-&gt;params['lineItem'];
    $globalPrices = craft()-&gt;globals-&gt;getSetByHandle('defaultPrices');
    $itemPrice = $globalPrices-&gt;fontStylePrice;
    $lineItem-&gt;price = $itemPrice;