I never paid to have my personal statement reviewed but I did submit it to some free service online (I'm sorry I can't remember which) and they actually gave me decent feedback. I also gave my personal statement to both vets I worked for, my parents, workshopped it in a professional writing class, and ran it past a few other random people as well. The more feedback (especially from those that know what it takes to get into vet school) is great. Also, your undergrad school probably has come kind of writing center where they will go over your personal statement with you and offer any suggestions so you should check that out too.