Sorry maybe this is dumb, but please don’t so easily take something someone else said or written to be the profound ultimate truth.
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Contributing to a relationship is not the same as a transaction. You already said it well with regard to sex, “it’s a shared experience”. A relationship is about being a team, a combined effort or partnership, not a transaction.
You are mistakenly calling a healthy relationship “transactional” when it’s actually reciprocal. Normal give-and-take that caring people just do without much thought, and it only becomes obvious when one person is taking advantage of the other.
You’re mostly just describing egalitarianism and decency in a relationship.