I bought a Honda Fit just to transport bikes with the rear seats down, as it has a flat load floor.
I can get five bikes in back, front wheel removed, staggered front to back. I sometimes buy two or three bikes at a time. Sellers will ask, don't you need a rack to get them home? I say, watch me. Never fails to drop a jaw or two.
Together with a Saris Bones rear rack, I've taken eight bikes total to swaps - five inside, three out.