There is not quite enough information here to be sure, but this article highlights transmission costs. This particular business model involves throwing around

There is not quite enough information here to be sure, but this article highlights transmission costs. This particular business model involves throwing around big chunks of data just in case they end up being needed and then handing them back out in response to potentially large numbers of requests. That would make this particular usage pattern fit to exactly what AWS is charging the most for. Also many alternative AWS services that can be used to speed up or simplify services are not really going to help with this case. So an alternative way of interpreting this is more along the lines of: We may have saved up to 80% of server costs by moving from AWS, but you almost certainly won't save that much even if a bunch gets spent on developing operations and tools.