The most expensive part of the framing process in most cases is going to be the frame portion. It would make sense to spend a little more time on this area because like the matting part, the choice in frame can make or break the look of the project.
The first decision would be what type of frame. Generally, there are two types of frames: wood or metal. There are many more varieties of frames in wood than metal. But if you're looking for more of a sturdy frame, metal might be the way to go. Another advantage of metal is the look and finishes. Some art work, mostly modern, works well with the texture and finish that the metal frames offer. Another advantage is the ratio of frame size to art size. Some large artwork works well if a very small frame is used. Since the metal frames are stronger for their size, a piece of art work that is 5 feet by 5 feet can be framed using a relative small metal frame because of the strength of metal.
Wood frames also offer just as many advantages as metal if not more. Though wood is not as strong as metal for its size, wood frames come in a wider range of sizes. Wood frames also offer many more textures. Wood frames often come with a small amount of detail on the top of the frame. This detail is usually done in clay and then laid into the frame, something that can't be done with a metal frame. Wood frames are also more expensive, due to the detailing and usually larger size.