Aerodynamic?

So the other day while we were roaming around town in the beautiful sunshine I saw this:

I did not take this photo (I found it through google).  Do you know what my first thought was?  "They totally have wasted what little storage capacity that car had!"  lol.  Yeah.... can you tell I like to haul a lot of stuff in my car?  It then made me think of this:

This was taken by my friend and used-to-be-coworker during a Mrs. Baird's national tour...errr something like that.  Nice wheels eh?!!  Pimpin'....

ANYWAY...  Can you imagine having to drive either of these cars on a highway?  I'm thinking they lack aerodynamics.  How many miles per gallon do they lose by adding 2 slices of bread to a Xion or a giant barrel of Red Bull to a Mini Cooper?  Yes, those are the things I contemplete... storage space and miles per gallon...