That only works if Microsoft sells the computer. Somehow, Microsoft wants to get paid for providing the operating system. I don't think that's unreasonable.
What's unreasonable is charging you for a computer that has Windows on it. If the same computer (or a better one) is offered with no OS at a price that's lower than the Windows machine by at least the OEM price of Windows, that's reasonable.
You could charge for the computer and separately for the OS, say 1 Euro. You could have the license in as pirate envelope and if you don't want it simply mail it back or return it to the seller, get your Euro, and don't activate any of the installed software.