This may be the easiest DIY iPhone repair and you can save a bunch of money by watching this video. It is important to not that this will not void your warranty. One of the few repairs that can claim that.
If you go to the Apple store they will charge at least $100 but I’m not positive. The average Cell phone repair shop will charge in the $60-$100 range. It is literally a 2 minute repair if you have the correct pentalobe screwdriver.
The back cover replacement parts generally runs about $20. So you are looking at saving a minimum of $40 and even save yourself time…honestly…then take 5 minutes to learn how.