Since you only want to calculate the average of all rows, you could forego grouping, and just use a WHERE
clause to compare the price against average. Code would be something like:
select item_name, item_price
from item
where item_price > (select avg(item_price) from item)
order by item_price desc, item_name asc
Of course, this assumes that you have only one row for one item_name
.