How much does an OEM WIndows 7 license cost?

For quite a long time, I have been wondering how much does the OEM Windows 7 license cost, because the ``free as in free beer'' of Linux for consumers may not be really appealing if they buy Windows via purchasing a new computer. 

Last night, I couldn't tolerate the poor graphic adapter of my Dell Mini 10 netbook any more. So i started looking for a replacement and I found this to answer my question:

The only differences between the two Dell Vostro 130's are the OS and hard drive. The price difference between a 250GB/5400RPM mobile hard drive and a 320GB/7200RPM mobile hard drive could be around $20 - if you buy online.

Conservatively, I would estimate the cost of a Windows 7 Home Premium OEM license is between $50 to $80. Please note that Dell will charge you extra $70 to upgrade from Windows 7 Home Premium to Business Professional.

Could 15 minutes of trying Ubuntu save you 15% on your IT cost? - For those who do not live in the US, don't get nervous if you can't feel this question funny.