As the two other comments here state, 20% is nothing to sneeze at when you are a low margin retailer (which many are). And I think 20% is the low end of possible savings (I'm the author of the post) - it's possible that the savings will end up being significantly higher, especially if retailers can keep some of the money in Bitcoin (because business partners start accepting Bitcoin and/or volatility comes down) and if fraud costs come down.