SELECT
	a.item_id,
	a.price,
	a.mod_id,
	a.compl_id,
	i.*
FROM  (
	(SELECT * FROM some_table p WHERE p.price >= 400000 GROUP BY p.item_id ORDER BY p.price ASC LIMIT 5)
	UNION ALL
	(SELECT * FROM some_table p WHERE p.price < 400000 GROUP BY p.item_id ORDER BY p.price DESC LIMIT 5)
) a
LEFT JOIN module_catalog_item i ON i.id = a.item_id
ORDER BY ABS(a.price - 400000) ASC
LIMIT 5