<p>Metrical is absolutely right.
AP Exams are considered rigorous, and benefit you in the admissions process. It shows that you challenged yourself by taking the class AND the exam.
Self-studying is even better. It shows motivation, determination, and skill on your part. Again, it only helps you.
Don’t take the exam if it’s going to break the bank, but if you can afford it, take it. Mention that you couldn’t take the exams for financial reasons in your apps.</p>