Fees don't depend on the processing capacity
If this capacity was held in just one pair of hands, it wouldn't work even it were virtually unlimited for obvious reasons. That would be a simple case of maximizing profits by just one player with no competition getting in the way. Conversely, if there were perfect competition, then the fees could be however small even if the processing capacity was limited, for example, by the network bandwidth. As you can easily see, these two extreme cases show it pretty clear that processing capacity as such is irrelevant to fees. In other words, fees depend on other factors, most important of which are costs and the level of decentralization (or the lack of such)