I used to work for the largest manufacturer of custom picture framing materials and no joke, the nicer moldings, mats and glass, expecially the conservation stuff can get really expensive! Great quality stuff but when I gave quotes for framing jobs I would do afterhours in the warehouse, even with my discount people were floored.
If I could toss out some thoughts.
Where you go and how much you invest should depend on the value of the print, where you are going to hang it and how long you want to keep it. Your chain craft stores always seem to have sales with coupons and have a wide array of options, but the quality of craftsmenship/materials may be lacking-get what you pay for. If you have a print of some value or preservation, I would get a couple quotes from local custom frame shops. And depending on your area, there are usually several to choose from so price shopping can be good.
Frames are always priced by the foot, except readymades(prefab'ed). Metal(aluminum) is always less then wood and if this is going in a nice room, I would suggest wood for the richness it can bring. The wider the wood, the more expensive. Natural wood frames w/o veneers seem to be the less expensive but warpage can happen. Wood veneer frames or gold/finished moldings are higher priced but have less warpage and look great. Some frames are merely laminated paper over wood. Cheap price, but could peal or warp with time. Also consider how you are going to hang it. I have seen some really nice framed pictures get hung with 4 screws right thru the frames into the wall. I guess if you have money to burn or in an enviroment that requires frames to not move, this is ok, but a good hanging kit is wise and structurally safe. Mats, glass and foamboard get just as pricey and complicated especially with conservation materials.
Poster size prints (24x36) being framed with average size wood molding, simple mat and basic glass can run in the area of $150.00-250.00. Metal frames are usually 1/3 to 1/2 that amount.
But, it doesnt hurt to shop around Biglots or other craft stores if you are budget minded.

Just thought I would share some of the experience.
ez