And when was the last time YOU bought a server with the primary goal of it being $200 cheaper than the power-guzzling slower alternative?
People don't buy individual servers any more, data centres buy heaps of them and people buy or rent capacity there. The owners of data centres, therefore, have a huge interest in the TCO of what they buy: price, density and energy demand are very important.
Most of the software stack is now available and for proprietary stuff ARM is the better platform anyway as it's easier to add dedicated stuff in silicon to boost performance and reduce running costs. ARM still lacks real oopmh for some jobs but it's current problem in the data centre is not having a standard firmware to make it easier to swap bits of kit in and out. We'll have to see if what ARM has promised on this works. On power/performance ARM is still ahead of Intel and the servers can be denser – the years of developing for mobile phones really do matter.
At the end of the day I don't really care what hardware my stuff is running on as long as works reliably. That Intel takes ARM seriously can be seen by the various products it's released over the last couple of years culminating in this. As with AMD's x64 this shows the market working. Once ARM-64 systems are available in number we can expect to see Intel reacting on price.
ARM's advantage over Intel remains the different business model. Instead of going after just AMD (and maybe Cyrix), Intel is facing a bunch of well-funded competitors and ARM itself is insulated somewhat from the struggle. Of course, the diversity has also held back the move into the data centre and Intel has some top notch people but I find the developments in the ARM architecture and manufacturing over the last few years far more impressive than Intel's rearguard action.