PostgreSQL aggregate over json arrays
Use the function for orders->'items' to flatten the data:
select elem->>'name' as name, (elem->>'price')::numeric as price
from my_table
cross join jsonb_array_elements(orders->'items') as elem;
It is easy to get the aggregates you want from the flattened data:
select name, count(*), sum(price) as total_value_sold
from (
select elem->>'name' as name, (elem->>'price')::numeric as price
from my_table
cross join jsonb_array_elements(orders->'items') as elem
) s
group by name;
Db<>fiddle.