You can find the code in file : app\code\core\Mage\Adminhtml\Block\Catalog\Product\Composite\Fieldset\Options.php
Mage_Adminhtml_Block_Catalog_Product_Composite_Fieldset_Options::getOptionHtml()
public function getOptionHtml(Mage_Catalog_Model_Product_Option $option)
{
$renderer = $this->getOptionRender(
$this->getGroupOfOption($option->getType())
);
if (is_null($renderer['renderer'])) {
$renderer['renderer'] = $this->getLayout()->createBlock($renderer['block'])
->setTemplate($renderer['template'])
->setSkipJsReloadPrice(1); // Here is the code to set value
}
return $renderer['renderer']
->setProduct($this->getProduct())
->setOption($option)
->toHtml();
}