That doesn't really make sense, as others have pointed out.
Imgur was indeed a valued customer, and we grew together and had a great relationship with them.
Customers like them helped us achieve the necessary scale to build out our network.
But pushing more bits costs more, not less ;)
though not as often today as in times past, there are points where 10Gbps is more expensive overall than 20 or 30Gbps.
Getting high traffic customers like Imgur allowed us to negotiate better commits, establish new peering and interconnection agreements, and otherwise lower the "unit costs" of the network we built.
It was generally never worth it to do this for free, but you're spot on that in certain cases it was worth it to do it for less than (current) per unit costs.
Ended up with KeyCDN for now
I could imagine that imgur traffic paid for itself.
How much is that additional 2Gbps of traffic (to Comcast) worth?