Does anyone know about how much these cost?

well it would depend on what you want to put it on, the thickness of the steel, the overall design and how many bells and whistles you wanted, Ive got a buddy that built a bumper for his 71 ford out of 1/4 in C channel for cheap, its plain and simple but it works

I would probably get a pre-made one for an '04 z71. I have a small dent in my bumper. Any chance I could just hammer it out or something?

If you're talking about hammering a dent out of a stock bumper... you may be able to depending on the size and location of the dent. You may be better off using a press of some sort if you can get at the dent with it off the truck. Hammering will probably crack the chrome plating (if it's chrome).

Good Luck!

I hear an alternate to hammering or pulling dents is using liquid nitrogen in small amounts directly on the affected area. Which would mean pulling your bumper, so you could keep the LN in the right place. If your considering replacing your stocker with an aftermarket bumper because of one little dent, consider that a burly 1/4 inch thick steel bumper will not dent easily, and if you do take a hard ream to the rear, that would dent it, it will put more stress on your frame, because there is no "crumple factor". This stress from being rearended could bend your frame, just something to keep in mind. As for prices, I know toyota tube bumpers are are 250 to 300, I have no clue about chevy bumpers. My best suggestion is do some searching online and see what you find.

If its a chrome bumper there may be a good chance that if you try to hammer the dent out the chrome will crack and start to flake off, and then eventually rust. But ive always liked the ranchhand bumper for newer chevy trucks.