I am pretty sure that at scale, the savings is so great that this is when you will tolerate a worse experience for cheaper gear. Hence Google and Facebook pinching pennies.

The advantage of buying Dell (or IBM) is that if you aren't buying enough computers to have your own dedicated people, you get someone to take care of you. Dell may be able to get you stuff faster, but the Taiwanese shops are also very good at having an agile supply chain.