You type in two cities you want to compare and 'wahlah.'
I come to find out my hometown of Denair is more expensive than my college town of Fresno. I would have to make more in Denair to maintain my standard of living than if I lived in Fresno, 13% more, meaning Denair is 13% more expensive than Fresno. Why is that? Housing. Housing costs 42% more in Denair than Fresno according to this site.
The site is addictive and fascinating giving users a statistical breakdown in over 100 categories.