From the code it looks like the object does not support the property.
function _isLabelForDisplayablePrice(label, scope) {
var g = self.data.general,
checkedPriceVals = g[scope + 'VehicleConfig'].displayablePrices(),
priceObjects = g[scope + 'VehicleConfig'].featuredPrices();
for (var i = 0; i < priceObjects.length; i++) {
// Find the parent object of the label field
if(label.name() == priceObjects[i].fields.label.name()) {
// Return true if displayable is checked
return checkedPriceVals.indexOf(priceObjects[i].fields.displayable.value()) >= 0;
}
}
// should never reach here, but just in case
return false;
}