They quite clearly said that it's not just grades that matter. Also, you'd show up to the exam so you don't suffer the university's consequences like academic probation and scholarship forfeiture, even if you were somehow "anti grade," whatever specious mindset you are envisioning.

Besides, I don't think anyone making their point would suggest that you shouldn't try to make good grades, which involves learning a subject well enough, including doing the boring work, to get a good mark.

I agree with them. If grades are the only thing you care about such that you'd be fine with paying an insider for a diploma without doing the work, then I'd say you wasted the entirely opportunity and only exercised your ability to cheat and be dishonest.