Attempting to list all product categories and the price range of all products within them

You can get using SQL query –

global $wpdb;
 $results = $wpdb->get_col( "
        SELECT pm.meta_value
        FROM {$wpdb->prefix}term_relationships as t
        INNER JOIN {$wpdb->prefix}term_taxonomy as tt ON tr.term_taxonomy_id = tt.term_taxonomy_id
        INNER JOIN {$wpdb->prefix}terms as t ON tr.term_taxonomy_id = t.term_id
        INNER JOIN {$wpdb->prefix}postmeta as pm ON tr.object_id = pm.post_id
        WHERE tt.taxonomy LIKE 'product_cat'
        AND t.term_id = {$term->term_id}
        AND pm.meta_key = '_price'
    ");

    sort($results, SORT_NUMERIC);
print_r($results);