Should I mention this in the Additional Information?

Hi, So I am applying to a lot of super competitive schools (WIlliams, Kenyon, Uchicago) where I know other applicants have taken lots of APs and courses. But due to my financial background throughout high school, my family could not afford to pay for the extra exams (my school follows the A-level system. I am an international student).
My stats are :1520 SAT, 4/4 GPA UW
However, my course rigor throughout high school is nothing extra. Its pretty average. My transcript doesn’t show much variation (my junior and senior year courses are all sciences with one Eng LIT). Should i mention in my additional info that this was due to my family’s financial burdens and not due to my unwillingness? In fact, I actually attended all classes for three extra subjects throughout my freshman and sophomore year and took online courses in junior year that all reflected my passions. I just didn’t sit for the official final exams of those classes since i couldn’t register (fees piled over $1000!). Whats even more aggravating is that I changed schools after sophomore year so my counselor and teachers dont know my previous background in order to mention in recommendations. So i have no proof of my extra classes taken.
Since a lack of apparent course rigor will most likely hurt my application to these competitive schools, do you think i should mention the financial limitations behind them? Or would that just sound like I am making excuses?

Yes, I think it is worth mentioning this.