When you purchase windows 10 cd then you pay 170 dollars.
but nowadays microsoft offer free upgradation of windows 10 online.
when you run windows 7 or windows 8 or 8.1 then you upgrade free of cost
windows 10 so download/upgrade your windows free of cost this offer will be
expire in august 2016 so quickly upgrade it. and enjoy....
There are many version of Windows 10 within 99$ to 499$.
Windows 10 Home is available in 119$
Windows 10 Pro is available in 199$
Even if you have old version windows you can upgrade it Free for 1 year.