We all know the saying, "You Can't Judge A Book By It's Cover".
In my opinion, you do. It doesn't mean the book inside is amazing if the cover is the best you've ever seen. And the same goes the other way.
However, with more and more people self publishing, the covers of books...the quality of the covers...seems to be going down. I can tell when someone uses a free stock photo then superimposes (is that the right word in the CGI world anymore?) a cat or a dragon over top. So, when I went out to find a cover for "Lane Changes" I went to a friend whose hobby is digital art, fantasy mainly but since LC isn't fantasy we are changing it up.
We have our background of a school hallway. Remember those lockers and all the times you spent hanging out at them? That's what we have and already I love it and it's not even 50% completed. We aren't talking about $ as this is fun for him and he's trying out his hand at book covers.
I feel that some people rush for their covers or maybe aren't familiar with other ways to get them, like through Fiverr. Fiverr is something I had never heard of until a friend--you can find her on Twitter at: @Talieee_d--told me that is how she found the cover for her book THE TAKERS, and I think it's simple and elegant and it cost her $5.
The hot covers now, for YA fantasy and romance, seem to be people on the cover looking introspective, are underwater, or are sitting with their back to the reader looking out over a sunset or ocean. I can't remember exactly when they went to this underwater theme as the first one I ever saw was a photo taken by my writer friend, and photographer Lani Woodland and she published it in 2014. Here is a link to her first book: Intrinsical, Book 1. She took this and the other photos in this series. She paid someone who is trying to put a portfolio together and got a dress on sale for her to wear.
So, there are other ways to get a cover and make it appeal to your reader. I know many people don't have money and the writing is a hobby but the cover is important; don't let anyone else tell you otherwise!