On March 1, the day after the first coronavirus death in the United States, brothers Matt and Noah Colvin set out in a silver S.U.V. to pick up some hand sanitizer. Driving around Chattanooga, Tenn., they hit a Dollar Tree, then a Walmart, a Staples and a Home Depot. At each store, they cleaned out the shelves.

Over the next three days, Noah Colvin took a 1,300-mile road trip across Tennessee and into Kentucky, filling a U-Haul truck with thousands of bottles of hand sanitizer and thousands of packs of antibacterial wipes, mostly from “little hole-in-the-wall dollar stores in the backwoods,” his brother said. “The major metro areas were cleaned out.”

Matt Colvin stayed home near Chattanooga, preparing for pallets of even more wipes and sanitizer he had ordered, and starting to list them on Amazon. Mr. Colvin said he had posted 300 bottles of hand sanitizer and immediately sold them all for between $8 and $70 each, multiples higher than what he had bought them for. To him, “it was crazy money.” To many others, it was profiteering from a pandemic.

The next day, Amazon pulled his items and thousands of other listings for sanitizer, wipes and face masks. The company suspended some of the sellers behind the listings and warned many others that if they kept running up prices, they’d lose their accounts. EBay soon followed with even stricter measures, prohibiting any U.S. sales of masks or sanitizer.