If you assume 25k MSRP on a base model Prius, and that the car will sell for $5k after 150k miles (absolute garbage offer - an actual number would be something like $10k-12k in today's market), then you get a worst case depreciation of 13 cents/mile. Let's say a Prius gets 45 mpg, gas costs $5/gal which gives you 11 cents/mile. Factor in tires and oil/brake fluid changes and maybe you get another $2k all in costs over the 150k miles, which is 1.3 cents/mile.

All in costs around 30 cents seems right. That assumes absolute worst case depreciation too. And don't forget, the government lets you deduct 58 cents/mile off your taxes, so you actually make a profit off every mile driven.