The prices might be low on all those Black Friday deals, but they hide a high cost for many workers.

Roughly half of all retail workers in the United States will be on the job Friday for the busiest shopping day of the year. If you’re picking up a marked-down TV or taking advantage of a 3-for-1 shirt offer, remember that the person helping you has likely been dealing for hours with long lines full of demanding customers. They are likely part of an understaffed team taking long shifts with no holiday pay or extra compensation.

And if they’re not one of the millions of retail workers logging a shift this weekend, then perhaps they are at the other end, filling orders under grueling conditions at Amazon fulfilling centers, which handle roughly half of all online retail orders in the country.

Amazon sold $7.9 billion worth of goods on Thanksgiving and Black Friday in 2017, and another $6.6 billion on Cyber Monday. To fill all those orders, workers must stay on their feet through long shifts, filling up 60 packages an hour per employee for up to 12 hours, their few breaks strictly coordinated and timed, their every move watched by supervisors who are forced to punish those who cannot keep up with the insane pace.

Despite the stress and time away from their loved ones, many retail workers are likely looking forward to the weeks ahead.

The busy holiday shopping season is a chance for them to pick up extra shifts to make up for the rest of year, when their work schedules are hit or miss. Many retail employees work under unstable schedules, sometimes not knowing they are working until as little as a day in advance, often seeing their hours fluctuate as much as 30 percent from week to week.

Sometimes they are forced to work split schedules or on-call shifts, making them set aside hours in their own day during which they are not paid. Sometimes they are sent home early when business is slow, taking away pay they were counting on.

With unstable schedules, workers find it hard to pay bills, or to take classes, schedule child care or fit in doctor appointments. The lack of sick or vacation time compound the problem. When they absolutely must see a doctor or take care of their child, calling out can mean they lose out on shifts later.

These circumstances, which are far more prevalent in large, national retailers than smaller local ones, are a recipe for unhealthy people. It also makes for unproductive workers, which is perhaps why some of the larger employers have taken steps toward making schedules more reliable, paid time off more accessible, and higher wages more attainable.

But many of those actions fall short of what is needed. Retail is the largest part of our economy, and we’ll always need workers to fulfill those needs, whether on the sales floor or in a warehouse. The people who fill those jobs should be able to support themselves and their families. They shouldn’t be worn down and out while their employers reap the benefits.