An 8" paper plate is about the right size target for center-of-mass hits in a personal defense situation. What I mean is, for that type of training and practice, there's no "bullseye" scoring and the target that you're practicing for doesn't have a bullseye printed on them either. That's the problem with the "Q" target and similar.
At stores, they can be had for one to two pennies each. If I'm going to miss it for some reason (maybe a new shooter or a difficult range for unaimed fire or whatever), I'll put it in front of a big sheet of corrugated cardboard to show the misses. For less dedicated shooters, kids and such, they're too boring. I like to have reactionary targets and stuff way more fun to shoot (there's a big list of those). But for the bulk of practice, paper plates gets the job done. I often set up four, five or six at different ranges and azimuths, and I can change them out often enough I don't have to mark my previous shots. I typically put them up with a big stapler and because they're stiff enough, one staple is all that's needed.
For my use, steel targets would have a great value, but they're costly. I can buy a lot of paper plates for the price of a steel target. My shooting ranges are temporary, so I have to setup and cleanup everything every time. Steel and the means to suspend it safely make for a more elaborate setup, but if anyone has advice on that, let me know. With the paper plates, I can staple it to brush or wood stakes or to a tall cardboard backer between two wood stakes or leaned against brush. They're light to carry, and take up no space at all in the vehicle which is scarce. I think to haul five or six steel targets and their supports, I'd have to use the truck. But I might get one.