Can someone help me find the cheapest deal for windows 7 ultimate OEM?

Hello all

I am starting up a computer sales business where I build the computers and install windows 7 on them to sell on Ebay and locally.
Currently I am researching the most cost effective way of getting hold of windows 7 legally (obviously) but for a low price.
I have scoured the internet for the OEM version of Windows 7 Ultimate only to find that the lowest price I could find was on Amazon at around £80.
I have found another website called Scan.co.uk of which sells the OEM for £134.03, but it eats way too much into my profits. (from this I would only be making
around £10 a computer).

can anyone find a deal that is cheaper than £80 at all or is it reasonable enough.

I was planning on making at least £50-£100 per computer.


Regards

Shozzy