“I can’t afford that” is a sentence about today
"I can't afford that" is almost always a sentence about today.
Said often enough, though, it stops sounding like a timing problem and starts sounding like a fact about you. That's the part worth arguing with.
A plan doesn't make anything cheaper. It just replaces a verdict with a schedule: this item, this amount, this rhythm, and a finish line you can actually see. Some things will still be out of reach, but far fewer than the sentence suggests.
What's the one thing you've been saying no to on reflex?