functions.php

add_action( 'woocommerce_admin_order_item_headers', 'wc_msrp_headers' );
function wc_msrp_headers() {
    ?><th class="item_msrp sortable"><?php _e( 'MSRP', 'woocommerce' ); ?></th><?php
}

add_action( 'woocommerce_admin_order_item_values', 'wc_msrp_order_item_values' );
function wc_msrp_order_item_values( $_product ) {
    $msrp = get_post_meta( absint( $_product->id ), '_msrp_price', true );
    printf( '<td class="item_msrp">%s</td>', ( $msrp ? wc_price( $msrp ) : '-' ) );
}