Snippet to add extra shipping cost to every UPS package. WooCommerce UPS Shipping Plugin: https://www.pluginhive.com/product/woocommerce-ups-shipping-plugin-with-print-label/

function.php

add_filter('wf_ups_rate', 'wf_modify_ups_rate', 10, 2);
function wf_modify_ups_rate($xml, $packages){
	$amount_to_add = 3; //change this with your value to be added with each packages
	
	if($xml){
		for( $i=0; $i<count($packages); $i++ ){
			//if negotiated rate
			if( isset($xml->RatedShipment->NegotiatedRates->NetSummaryCharges->GrandTotal->MonetaryValue) ){
				if( property_exists($xml->RatedShipment->NegotiatedRates->NetSummaryCharges, 'TotalChargesWithTaxes') ){
					$xml->RatedShipment->NegotiatedRates->NetSummaryCharges->TotalChargesWithTaxes->MonetaryValue += $amount_to_add;
				}else{
					$xml->RatedShipment->NegotiatedRates->NetSummaryCharges->GrandTotal->MonetaryValue += $amount_to_add;
				}
			}

			// if normal rate
			$xml->RatedShipment->TotalCharges->MonetaryValue += $amount_to_add;
		}
	}
	return $xml;
}