On average, Walmart workers come up considerably short, earning just $13.85 per hour compared with Costco's $24.50 per hour.

Walmart executives argue that raising workers' wages doesn't solve their money management problems. The app, called Even, connects to workers' bank accounts and calculates how much money they have to spend between paychecks to cover household and other expenses. One thing the app can't do, of course, is make small paychecks cover large expenses, even if workers can get to the money early.

And it's not as if it doesn't cost employees to take advantage of early access to pay, even as the practice is spreading. Other high-profile employers, mostly retailers and restaurant chains such as McDonald's, Uber and Outback Steakhouse, now allow workers to access their pay on a same-day basis through apps. But even though employers pick up the cost of some services, employees can be charged as much as $3 a day to access their funds.

And since low-wage earners likely find instant access attractive, it can end up costing them far more than the benefit is worth.

Says HRDive, "It may be an assumption among Walmart and other companies offering same-day pay benefits that workers' money management skills will be positively affected by the service. But employers should be cautious about adopting programs or services focused solely on what they think employees might be doing incorrectly," adding, "Financial wellness is no longer something for which HR can shirk responsibility. Statistical evidence is clear in showing a drop in workers' financial well-being as well as a growth in the amount of debt owed, the latter particularly caused by student loan debt."