SELECT
"product cost".cost                            Cost,
"product price".price                          AS Price,
"product price".price - "product cost".cost    AS Revenue,
Greatest("product cost".START DATE,"product price".START DATE) AS START DATE
Least("product cost".END DATE,"product price".END DATE) AS END DATE
FROM   "product cost" INNER JOIN "product price"
ON "product price".id = "product cost".id
WHERE
Greatest("product cost".START DATE,
"product price".START DATE) < Least("product cost".END DATE,"product price".END DATE)