In the quest for a higher minimum wage, how high is too high?

In 2014, Seattle voted to gradually hike its minimum wage to $15 an hour, with the rate jumping from $11 to 13 last year. Yet on average, low-wage workers have made $125 per month less.

That's a key result of a new University of Washington study that found that the hourly wage hike could in fact be costing jobs. The study, released last week, examined low-wage employment within the city of Seattle from 2014 to 2016.

"What we found," study co-author Mark Long explained to CNBC's "On the Money" recently, "is that employees increased wages, which you'd expect given the mandate of the law, but they also cut hours and they cut jobs."

Long, a professor of public policy at the University of Washington, added that as a product of fewer hours and available jobs, "the net amount paid to low-wage workers declined instead of increased."

The findings come as many states and cities are passing new regulations to mandate a minimum wage increase over the next few years. Nationally, fast food workers are among those actively seeking a $15 and hour minimum pay, and labor unions are organizing a "Fight for $15" push.