Yes, and package delivery autonomous car can be made very small -- just big enough to carry the package. In fact, a ground-based autonomous delivery vehicle doesn't have to look anything like a car. Imaging an autonomous Segway-like 2-wheel cart. Segway is 4.5 times more efficient that Toyota Prius and 11 times more efficient than average American passenger vehicle.[1] Something like that would allow delivering packages very cheaply.

[1] http://www.segway.com/downloads/pdfs/energy_efficient_segway...