function custom_discount_amount_sale_badge( $html, $post, $product ) {
if( $product->is_type('variable')){
$amount_off = array();
$prices = $product->get_variation_prices();
foreach( $prices['price'] as $key => $price ){
if( $prices['regular_price'][$key] !== $price ){
$amount_off[] = $prices['regular_price'][$key] - $prices['sale_price'][$key];
}
}
$amount_off_s = "up to -$" . round(max($amount_off));
} else {
$regular_price = (float) $product->get_regular_price();
$sale_price = (float) $product->get_sale_price();
$amount_off_s = "-$" . ($regular_price - $sale_price);
}
return '' . esc_html__( 'SALE', 'woocommerce' ) . ' ' . $amount_off_s . '';
}
add_filter( 'woocommerce_sale_flash', 'custom_discount_amount_sale_badge', 20, 3 );