Cost is (Almost) entirely up to you.
Well of course, your costs will depend on your particular style of travel. For some estimates, Motel 6 rooms can be had for around $75 a night.You could stay at a camp ground and spend less, or at an upscale hotel and spend a lot more. You can get a pretty good handle on fuel costs by using the Road Trip Fuel Cost Calculator and get more ideas on saving money from Bob and Gen's Art of the Cheap Road Trip. I'd count on around $100 for admissions to various things, but, again, that's largely under your control.
AZBuck