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 (31,32,33,34,35,36,37)
) 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: 709 — title: Lagoon 42 - White Lotus — meta: ['']
ID: 741 — title: Fountaine Pajot Lipari 41 - Bella Alla — meta: ['']
ID: 773 — title: Fountaine Pajot Belize 43 - Kindred Spirit — meta: ['']
ID: 805 — title: Leopard 45 - Sunsail 22 — meta: ['']
ID: 835 — title: Lagoon 620 - Dream Escondida — meta: ['']
ID: 856 — title: Lagoon 42 - Moonrise — meta: ['']
ID: 888 — title: Custom Built 111 - Party 111 — meta: ['']
ID: 920 — title: Astondoa 102 - Blosson — meta: ['']
ID: 952 — title: Redemption Prem — meta: ['']
ID: 711 — title: Dream 82 - Dream 82 — meta: ['']
ID: 743 — title: Lagoon 400 S2 - Blue Coco — meta: ['']
ID: 775 — title: Lagoon 421 - Ms Coco — meta: ['']
ID: 807 — title: Leopard 45 - Moorings 23 — meta: ['']
ID: 836 — title: Leopard 42 - Sunsail 23 — meta: ['']
ID: 858 — title: Tropical 36 - C'est La Vie 2 — meta: ['']
ID: 890 — title: Custom Built 39 - Katapult — meta: ['']
ID: 922 — title: Azimut 55 - After 8 — meta: ['']
ID: 681 — title: Bali 4.5 - Proclus — meta: ['']
ID: 713 — title: Lagoon 620 - Dream Carolina — meta: ['']
ID: 745 — title: Lagoon 440 - Blue Nicobar — meta: ['']