From a suppliers point of view you could be describing Woolworths and Pick'nPay here.Not sure if this will be good or bad. Have read lots of views on how Walmart is not great towards producers. Have seen a few articles from food producers saying how Walmart will bully them into dropping prices to the point were they can't even make a profit anymore putting them at risk of closing down. Producers are forced in the USA to accept it as in America they are such a huge part of the supply chain if you get cut off from Walmart you struggle to get your produce to customers. Nasty business to deal with if you are a supplier overall.
Amazon is even worse. Thousands of stories out there about how they scalp independent people's products. Saw an article about a designer who created a very popular new hand bag. Hand made quality stuff. She started selling on Amazon and within a few months Amazon had an exact replica selling much cheaper than hers that the Amazon factories in china produced. Put her out of business. Tried to sue them and failed as they had better lawyers and money to delay things in the courts until she had to withdraw due to lack of funds.
Amazon and Walmart very actively destroy a countries small producers and then take their profits and run. Really doubtful they will be a net benefit to the SA economy if they actually get big.