SELECT * FROM `wp_postmeta` WHERE `post_id`=73 AND `meta_key`='_regular_price' OR `meta_key`='_sale_price'
`post_id`=73 AND `meta_key`='_regular_price'
либо такие `meta_key`='_sale_price'.
`post_id`=73 AND (`meta_key`='_regular_price' OR `meta_key`='_sale_price')