The quotes you're getting are that high because gasoline prices are that high (at least what I'm paying).
It's about 30 hours round trip for you, right? Cost to drive, IF you get 30MPG @$5 a gallon, then it will cost $300-350 in gas. If you get just 20MPG...like with a minivan, then a 30 hour trip will cost more like $500. "Saving.org" has a road-trip gas cost calculator.
If it's just a CB750 frame, with no swing-arm, no triple-clamp attatched, it will fit into the back seat of many* commuter cars, provided you put moving blankets or thick, old blankets on the backseat beforehand. Really. Make sure both ends don't touch the uphoulstry, because that black grease won't come out. (Cough, cough...I heard that somewhere) If the swing-arm is attached to the frame, then you'll likely need a minivan or pickup. Minivans don't get great MPG usually, but they're big. Also, minivans have more windows to open if the frame stinks of old grime.
*Note: I don't know diddly-squat about the backseat sizes of new cars. You'd have to measure.
