This assumes that you can evenly distribute your transcoding load over the course of a month. For most customers, transcoding needs are severely peaky - 10x or more from peak-to-average. So you either buy for the peaks and your hardware goes idle 90% of the time, or buy for the average and see long queue times. For most video publishers, each on-premise machine ends up using only a small fraction of 43,000 minutes each month.