Re: really!
Maybe, but the £400 a seat difference is three-quarters of f*ck all compared to the total cost of running 300 boxes in an enterprise. Staffing, software, 24/7 support, servers, bandwidth, peripherals, etc. Over three years it's pennies per seat, per day. Rounding error, in other words.
If you have a half-way compelling reason that Macs offer an advantage over PCs for your particular business, then the cost difference is so small as to be an irrelevance.