Raised prices. The company I work for alrady has to pay a 3% charge on payment returns. Take 3% of the product price, multiply by the expected rate of return, and add that as a hidden fee to the new product price.
Everyone pays more for everything the retailer sells until their revenue and costs ratios match roughly as they did before, with variation depending on competition intensity and elasticity of the products sold.
Everyone else that bought something at the higher prices covers the fees when the much smaller number of people request the refund. So it is essentially crowd funded