Since we need a computer for the server and all ten workstations, we are going to ignore the cost of the hardware. Since some kind of productive work will probably be done, we need to assume some kind of application software. On the Windows workstations we will assume Microsoft office and StarOffice on the Linux machines. I realize that this is also an unfair comparison because as StarOffice is more useful powerful and has more features than Microsoft Office. However, Microsoft has yet to do a port of MS-Office to Linux.
Administration is just one addition aspect, but the purchase of updates also needs to be included.
Upgrades for Windows NT are typically half the price of a new copy. However, even if your just upgrade the server, you must still upgrade the client access licenses for every workstation. Sometimes you want or need to just upgrade a single component. Microsoft's monolithic structure does not allow this. Instead, you are forced to upgrade the entire system.