It sounds like you want Consumer Price Indices for Food and Beverage for various metropolitan areas. The Bureau of Labor Statistics calculates just such indices: http://download.bls.gov/pub/time.series/cu/cu.txt
Metropolitan Areas
area_code area_name
A101 New York-Northern New Jersey-Long Island, NY-NJ-CT-PA1
A102 Philadelphia-Wilmington-Atlantic City, PA-NJ-DE-MD
A103 Boston-Brockton-Nashua, MA-NH-ME-CT
A104 Pittsburgh, PA
A207 Chicago-Gary-Kenosha, IL-IN-WI
A208 Detroit-Ann Arbor-Flint, MI
A209 St. Louis, MO-IL
A210 Cleveland-Akron, OH
A211 Minneapolis-St. Paul, MN-WI
A212 Milwaukee-Racine, WI
A213 Cincinnati-Hamilton, OH-KY-IN
A214 Kansas City, MO-KS
A311 Washington-Baltimore, DC-MD-VA-WV
A316 Dallas-Fort Worth, TX
A318 Houston-Galveston-Brazoria, TX
A319 Atlanta, GA
A320 Miami-Fort Lauderdale, FL
A321 Tampa-St. Petersburg-Clearwater, FL
A421 Los Angeles-Riverside-Orange County, CA
A422 San Francisco-Oakland-San Jose, CA
A423 Seattle-Tacoma-Bremerton, WA
A424 San Diego, CA
A425 Portland-Salem, OR-WA
A426 Honolulu, HI
A427 Anchorage, AK
A429 Phoenix-Mesa, AZ