If you shoot on x-ray film, you can get it down to 20-ish cents a shot. Then, when you're good, you can shoot the expensive stuff.
Anyways, don't get into 4x5. Spend time pouring over photography books and manuals. Read Ansel Adams' series of instructional books. Then, when you have a lot of theory down, do some digital. After all that, try some 4x5.