At least in the USA, Dell offers the choice of Windows 7 or Windows 8 on PCs bought through their Home Office and Small Business site. There is no cost premium for buying with Win 7 installed. I have had no problem buying just a single PC through that site.
I know of a commercial outfit which has replaced one-third of its administrative computers, The new computers were purchased from Dell and they recently arrived. Like a lot of businesses, they bought the PCs with Win 7 installed, since they didn't want the retraining costs and downtime that going to Win 8 would entail.
seacue