Anyone who makes their own covers and/or ads with a visual component should take advantage of deals like that. Good photos can be expensive.
On individual photo prices, those typically depend on whether you're buying ala carte or have an image plan from the company. Most people probably wouldn't need a huge plan, but the biggest Shutterstock monthly plan brings cost per image down to something like $0.26. So if you're a graphic designer, there are options that will work for you. If not, it's still sometimes worth checking the pricing to see what options are available. Consider how many images you'll need during a given period of time vs. what you'll have to pay for them. You probably still won't get as good a deal as this Deposit Photo deal, but sometimes if you really love a particular image or group of images, it's worth checking to see what deals might be available.