[Porsche-O-Phile]

I have a Thule that I got at REI. Very good quality but I don't know that it would necessarily count as "cheap".

I know it's a pain to pile them in the back but if you get some big heavy blankets (those padded things that furniture movers use would be great if you can find some) that'd help a lot and be a lot cheaper - you could probably stack the bikes in the back without too much worry about damage.