Mike you make some good points.
Edmunds lists 17 cars for under $15K:
http://www.edmunds.com/apps/vdpconta...bute2=under15k

Many base models are around $10,000 and would be a good choice for an excellent dollar-for-mile car, and some are rated mid-30's MPG.

One note however as soon as one begins to add options to the base models the dollar-for-mile benefit quickly shrinks.