Any expert can help me verify how to correct this SQL answer ?

select art_title,purchase_price from artist,CUST_ART_ORDER where artist.ARTISTID=CUST_ART_ORDER.ARTIST_ID and customer_id=1 and purchase_price>ALL(select avg(purchase_price) from CUST_ART_ORDER where customer_id=1)

hit error Error 1: could not prepare statement (1 near "ALL": syntax error)

*Question is

List all the items with a price above the average price for a particular customer.