I studied Google's file system. What Google figured out is that, with the rise of very fast networking such as 10 Gig Ethernet and faster, the network is much faster than local disk. Files were spread across multiple servers so they could all stream different parts of the file off their local disks simultaneously to the client computer faster than the local disk on any one computer could run. Thus, you could have systems like Gmail that could run much faster than even local disk based email clients, even with thousands of users.

Other providers were probably using expensive NASs with huge profit margins built in. Google was using thousands of the cheapest crappiest commodity parts because it was all triple redundant... and it worked faster because the network was really fast and multiple computers could stream different parts of the same file to clients.