Should I accept the price if I was the only one playing?

Think of it like this: By entering the contest you've given them rights to use your work. They may not have attracted the greatest talents on the planet (I'm assuming here), but if you refuse it's still something for nothing. Only if you have some ethics against receiving recompense (wouldn't recommend, starving artist still is the general situation), or the contest had rules against a single applicant.
Besides, if it doesn't give the other students something to admire, they'll probably come up with amusing cynical remarks. No loss, either way.