So the real question is are you paying for the developers / artists service (ie paying for their time) or are you buying the product itself? That's a discussion that has to happen between the customer and the company selling their services.
For what it's worth, I've used photographers and other creative services before where they only charged one flat fee and you retained copyright ownership on anything produced. I have also worked at web shops where the company retained ownership of the code, however in that instance we also did the hosting, support, etc so we provided the service. Essentially SaaS but before SaaS really took off as a buzzword.
