optimize sum array array of objects by key in postgresql - arrays

Question

I need a postgresql function that merge and sum (by key) 4 jsonb array of objects. Each jsonb can have 0 or multiple objects:
parameter 1: [ {"a": 1.0}, {"b": 2.5} ]
parameter 2: [ {"a": 1.0} ]
parameter 3: [ {"a": 1.0}, {"c": 2.5} ]
parameter 4: [ {"a": 1.0}, {"b": 2.5} ]
and the result expected is this:
[{"a": 4.0}, {"b": 5}, {"c": 2.5}]
I have a function that actually does that. But it's performance is very poor. I need to call it for each row. At this moment, with 1.4 millions of rows, the difference adding the function call is from 39 sec, to 2 min 30 sec. we expect to raise about more than 50 million of results, and that will be about 1 hour 40 min aprox.
I'm really new to postgresql and this is the best function I can do. I don't know if there is a more effective way to do this.
this is my actual function.
create or replace function join_and_sum(parameter1 jsonb, parameter2 jsonb, parameter3 jsonb, parameter4 jsonb) returns jsonb
language plpgsql
as
$$
DECLARE
column_jsonb jsonb;
BEGIN
select into column_jsonb jsonb_agg(p.jsonb_build_object)
from (
SELECT jsonb_build_object(key, SUM(value::float))
FROM (
SELECT (JSONB_EACH_TEXT(j)).*
from jsonb_array_elements( parameter1 || parameter2 || parameter3 || parameter4) j
) j
group by j.key
) p;
RETURN column_jsonb;
END;
$$;
thanks in advance