I wasn't sure what reviews/ratings meant, so didn't check it, but review average does have an effect on me. If a book has a lower average than mid-3s I tend to look elsewhere.
Anyway, maybe I'm an anomaly, cover has almost no effect on me except to turn me away occasionally. For instance, I avoided a certain dog mystery series for years because of the ridiculous, inaccurate portrayal of a dog on the cover. Can't remember if the cover changed before I finally bought it or if I just got desperate for something to read one day, but it became a favorite series.
Title also can have an effect. The whole reason I ever started James Lee Burke's Robicheaux series was the title "A Stained White Radiance."
Those were unusual reasons, though, usually genre comes first as I only read certain ones. After that blurb, then the first few pages.
Price factors in that I won't buy a new-to-me author unless it's a very good blurb and a very reasonable price, yet free and $.99 evoke my mother's voice saying, "You get what you pay for."