Where did you read that? That number sounds way off for just the fence itself. A new cedar fence might add some value, but $7k is more like the total cost of installing it. The added value to your home is usually a lot less, maybe a couple thousand if you're lucky. I've seen people spend that much hoping to get it all back at sale, and they're always disappointed.
People forget how much a good fence can change the feel of a yard. A neighbor of mine had a sagging chain link, replaced it with a clean wood fence, and their whole backyard looked bigger and more private. It's not just about the sale price, it's about making the place look put together so buyers don't see a project. That can make the difference between a quick offer and the house sitting for months.