"Nullify" the top seller query, within the WooCommerce Status dashboard widget (might be helpful, until such time as the query results are cached).

woocommerce-802-kill-top-seller-query.php

<?php

/**
 * The top-seller query (used for the WooCommerce Status dashboard widget)
 * runs on every dashboard request.
 *
 * It can effectively be nullified using this snippet, if the performance
 * impact is too great.
 *
 * (Tested with WC 8.0.2)
 */
add_filter( 'woocommerce_dashboard_status_widget_top_seller_query', function () {
	return [ 'SELECT NULL' ];
} );