“I can’t afford that right now” is a complete sentence. Good friends will find a cheaper plan.

Money is one of the few limits people apologise for having, as though being broke were a flaw in your character rather than a fact about this month. Saying it plainly also spares you the elaborate excuses, which are harder to keep straight and leave your friends guessing why you keep bailing. Anyone worth your weekend would rather change the plan than lose you from it.

Say the short true thing when something costs more than you have, and propose the cheaper version in the same breath. Suggest the park, your kitchen, the earlier showing. The ones who push anyway have told you something useful.