Postgres Jsonb aggregation

You can consecutively use JSONB_POPULATE_RECORDSET() along with creating types for each JSONB columns and then JSONB_BUILD_OBJECT() to combine the key value pairs while summing up the numeric values such as

WITH t0 AS
(
 SELECT city, 
        (JSONB_POPULATE_RECORDSET(NULL::jstA,JColA)).*,
        (JSONB_POPULATE_RECORDSET(NULL::jstB,JColB)).*
   FROM t
), tA AS
(
 SELECT city,
        JSONB_BUILD_OBJECT('id',id,'name',name,'type',type,'amount',SUM(amount),'full_name',full_name) AS jsA
   FROM t0
  GROUP BY city, id, name, type, full_name
  ORDER BY id
), tB AS
(
 SELECT city,
        JSONB_BUILD_OBJECT('key',key,'value',SUM(value)) AS jsB
   FROM t0
  GROUP BY city, key
  ORDER BY key
)
SELECT *
  FROM (SELECT city, JSONB_PRETTY(JSONB_AGG(jsA)) AS AggJsonColA FROM tA GROUP BY city) AS tA
  JOIN (SELECT city, JSONB_PRETTY(JSONB_AGG(jsB)) AS AggJsonColB FROM tB GROUP BY city) AS tB
    ON tB.city=tA.city

Demo