Do you mean like stock photos?
Depends on the type of copyright that you need, but usually companies buy stock photos in bulk, which is how they get em for less than a dollar each. If you just want one single stock it'll probably be about 5-10 dollars (depends). If you have an Adobe Account I believe you get a certain amount of free stock images you can use as well as part of the deal. Some stock companies will make you leave their logo on the stock, other's don't.
The only time I've used it is for graphic design companies, so I never actually purchased it myself--just made them do it, and they had a package so they didn't really care how many I made them get.