<?php

class MyCustom_Module_Model_Observer
{
    public function urapidflow_product_import_after_fetch($observer)
    {
        $vars = $observer->getEvent()->getVars();
        foreach ($vars['new_data'] as &$row) {
            if (strpos($row['weight'], 'kg')!==false) {
                $row['weight'] = intval($row['weight']);
            } elseif (strpos($row['weight'], 'g')!==false) {
                $row['weight'] = intval($row['weight'])/1000;
            }
        }
        unset($row);
    }
}