Car covers are good for long-term indoor and shorter-term outdoor storage. When a car cover is used outdoors, moisture can get trapped under the car cover and that can cause damage. And in extremely cold weather, the cover can stiffen up and snap in the wind, causing scratches.
As for pricing, a Toyota FJ Cruiser car cover will typically cost you between $100 and $300, though you’ll find covers outside of that range. You shouldn’t need anything too fancy for indoor storage, though for outdoor storage you’ll get what you pay for. It’s always best to shop around and find something that suits your budget and needs.