Mike

add_filter( 'woocommerce_get_price_html', 'override_default_price_html', 100, 2 );
function dw_change_default_price_html( $price,$product ){
    if ( $product->price > 0 ) {
      if ( $product->price && isset( $product->regular_price ) ) {
        $from = $product->regular_price;
        $to = $product->price;
        return ( ( is_numeric( $to ) ) ? woocommerce_price( $to ) : $to ) .'<span>'. ( ( is_numeric( $from ) ) ? woocommerce_price( $from ) : $from ) .' </span>';
      } else {
        $to = $product->price;
        return '<span>' . ( ( is_numeric( $to ) ) ? woocommerce_price( $to ) : $to ) . '</span>';
      }
   } else {
     return __( 'Free!', 'woocommerce' );
   }
}

<span class="price"><?php echo $price_html; ?></span>

<span class="product_price"><?php echo $price_html; ?></span>

@media screen and (max-width:480px){
    .woocommerce ul.products li.product, .woocommerce-page ul.products li.product {
        width: 42.5%;
    }
}