Derek’s particular world view seems to see most relationships in transactional terms, including sexual relationships.
Depends on your definition of "transactional". In the widest sense, if we extend the meaning of "transactions" to companionship, fulfillment of emotional needs, even attraction, then yes, (almost) all romantic/sexual relationships are transactional. Almost nobody would stay in a relationship lest there is something in it for them.
But even restricting it to what most people mean by that term, things like better standard of living, gifts, K1 or spousal visa, many relationships are still transactional. Especially when you have a big difference in age or attractiveness between the partners.
I will leave you with some wisdom from Larissa:
"The wife[sic] are the most expensive prostitutes ever, darling".