Vile said:
This is definitely where the house rule needs to come in and create a (low) flying car as opposed to an orbital insertion car.
But then you are changing the base setting - gravity drives
can get you to orbit. If you want to change gravity changes in YTU, then by all means it's yours. Simply add a cheap,'Low Altitude Gravity Drive' with a flight ceiling and perhaps 1/3 the price.
The gravity drives of the Traveller setting have always been able to get you to and from orbit. That doesn't mean every gravity car was intended for such duty. Many light aircraft made today
could make Trans-atlantic journey's, but that doesn't mean they were intended to do so.
Supplement 5 has an air/raft (completely intended to go to orbit, it needs to as part of many small starcraft's equipment) and a few cheaper "grav cars". The cheaper grav cars have grav drives, so they
can get to orbit, but it doesn't appear to be their intention. These cars appear to be closer to the 5th Element speeders you desire, not the air/raft.
Possible Solution:
You don't necessarily need a house rule with Supplement 5 to create cheaper flying cars that aren't going to get you (alive) to orbit. Design some flying cars using lift drives combined with a jet. The lift allows the car to hover in place while the jet gives it speed. This will leave you with less room in your flying car, but it will also make it
much cheaper. Leave out expensive life support and your flying car can't go into orbit (well it conceivably could, but it would kill the driver and passengers). Just a guestimate, but you could make a small 4m3 flying car for around 40,000. Such "lift jet cars" could solve everyone's problems (it's cheap and not intended for orbit).