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: 707 — title: Lagoon 560 - Seven — meta: ['']
ID: 739 — title: Leopard 40 - Moorings 20 — meta: ['']
ID: 771 — title: Lagoon 400 S2 - Eos — meta: ['']
ID: 803 — title: Seawind 1000 - Dreamcatcher — meta: ['']
ID: 834 — title: Leopard 45 - Sunsail 23 — meta: ['']
ID: 854 — title: Lagoon 420 - Bluecastle — meta: ['']
ID: 886 — title: Custom Built 56 - Grand Poseidon — meta: ['']
ID: 918 — title: Integrity 55 - Adamo — meta: ['']
ID: 950 — title: Azimut 76 - Scooby Doo — 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: ['']