About $300 nine years ago. Two weeks in Zion, Bryce, Grand Canyon, Canyonlands, Arches, Great Basin NP.
Entry to NP was free due to the annual pass I had. Car rental was about $100, the rest was lodging, gas and food. We had really good time, however my wife from time to time reminds me that I dragged her hiking in Arches when it was 110F in shade.