You are being told that crypto payment processing would cost you a 0.5-1.0% fee. However, this includes only the processing with no real conversion into something stable. In the end, you can end up with many different coins that you don't know the actual value of, and given Bitcoin price's ups and downs, you can't really evaluate if you have made any money and what the actual margin of your product/services is.
Then you get another 2-3% in exchange for something stable like EUR or USDT. And if you would like to convert it back to crypto in order to send someone a crypto payment, you need to pay another 2-3% for the exchange. So you end up paying at 4.5% in the best-case scenario. Now let's include the indirect pricing that doesn't directly affect your money, but it has an impact on your customers big time.