SQL запроса:

SELECT   wp67_posts.*
					 FROM wp67_posts  LEFT JOIN wp67_term_relationships ON (wp67_posts.ID = wp67_term_relationships.object_id) INNER JOIN wp67_postmeta ON ( wp67_posts.ID = wp67_postmeta.post_id )
					 WHERE 1=1  AND ( 
  wp67_term_relationships.term_taxonomy_id IN (3,4,5,6,298,299)
) AND ( 
  wp67_postmeta.meta_key = 'average_price_week'
) AND wp67_posts.post_type = 'boats' AND ((wp67_posts.post_status = 'publish'))
					 GROUP BY wp67_posts.ID
					 ORDER BY wp67_postmeta.meta_value+0 DESC
					 

Первые 20 постов и meta:

ID: 1185 — title: Penelope — meta: ['2333.6']
ID: 1175 — title: Pinson — meta: ['9660']