I get paid $200 (by my publication, not the writer) to write an approximately 1000-word in-depth review. So, even laying aside the ethical issues here, I could never pay $425 for a capsule review. It seems wildly overpriced. I wonder how much of that the review's author receives.
And when I see a Kirkus blurb on a self-published book, all I know for sure is that the author had deep pockets. I'm not saying the reviews aren't honest, but a paid review is a strange thing. It may not lead to insincere glowing appraisals, but it could cause punches to be pulled here and there, or boring books to be dressed up with bland praise, if the writer feels any pressure not to be negative. (That said, the pressure can exist in regular journalistic reviewing, too, and is why people often decline to review things they know they won't like.)
In my experience, anyone at a general interest publication (or blog) who agrees to review a self-published book is doing it because they like the book, even love the book. No one has a shortage of books to review, even sorta OK books. No one will waste time picking apart some poor writer's bad self-published book. (Old Hack's blog is different because it's specifically focused on giving straight talk to the good, bad and ugly of self-publishers -- a very useful function IMHO, but not one most publications can serve.)
So, instead of paying for a review, I'd write the best book I could, revise the hell out of it, then cast a wide net until I found a blogger or other reviewer who loved it enough to want to tell his or her readers about it. No substitute for sincere enthusiasm.