We perhaps only disagree on what is "server-grade" vs what is sold for servers.

Google, for example, are famous for making big data centres out of cheap commodity boxes, and I double Amazon are any different. I certainly know the rackspace blades I've played with didn't make my grade of either! :)

I can't make any claims to contrary about other providers, but I know at the very least that at one point not in too distant past the primary systems used for Rackspace Cloud hypervisors were Dell R720 rackmount servers. Maybe not the most amazing hardware, but considering how common they are you can hardly refuse to say they're "server-grade". The newer OpenCompute stuff is also clearly well-made hardware.

Everything I've read implies that cheap commodity servers like Open Compute are just as reliable as name brand Intel servers (not surprising considering that they're made from the same parts), and ~95% of the market appears to be satisfied with that level of reliability.