EGGS over easy, home fries, bacon and toast. It’s $9.99 at Tops Diner in Newark but $5.79 at Pop’s Diner near Oklahoma City. If the same meal in two parts of the country has such a different price, should America have a single national minimum wage?

As recently as three years ago, Democrats led by President Barack Obama had settled on pushing a national minimum wage increase to $10.10, up from $7.25, which was set in 2009. Since then, a movement working on behalf of low-wage workers has pushed for a $15 national minimum wage in what is known as the Fight for $15. This noble movement has succeeded in several high-cost cities, including New York, San Francisco, Los Angeles and Seattle, where wages are set to rise on a glide path to $15 in several years’ time.

But a wage floor that is right for the high-cost coasts may be the wrong fit elsewhere. After all, in a 2016 report we noted that a typical dentist appointment in Jackson, Tenn., ran $67, but it was $108 in San Francisco. A dozen eggs was $3.99 in Oakland, Calif., but 93 cents in Fargo, N.D. And according to the real estate website Rent Jungle, a two-bedroom apartment in the Los Angeles metro area runs $2,907 per month. In Philadelphia it’s $1,739; in Jacksonville, Fla., it’s $1,112.

Seen in this context, the fight for $15 makes more sense for people living in Brooklyn, where parking can run $30 a day, than it does for people in Cumberland, Md., where a space costs $35 per month. And it explains the very different minimum-wage levels that have been set in different states. In 2014, in addition to Seattle and San Francisco’s vote for $15, Arkansas, Alaska, South Dakota and Nebraska all chose to raise their minimum wages. In these four rural, lower-cost states, the new minimum wages rose to between $8.50 and $9.75.