I understand your argument. I still think it's excessively reductive. There's way more to even the sexual dimension of a marriage than just this tit-for-tat ethos you've outlined.

Sex is the mutual gift of self, in both directions. It's not the wife giving herself up for her husband to take. It's the husband giving himself wholly and unreservedly, and the wife receiving that and giving herself wholly and unreservedly back to him.

There's a sense in which that dynamic is an echo of our relationship with God, but that's a whole different conversation.