I offer any key from my MSDN subscription account prices for specifics are listed below (if you see an MS key that is not listed below please PM me and we can discuss). Escrow is allowed as well if necessary

Windows 8.1 Professional : $4
Windows 8 Professional : $3
Windows 7 (Professional, Ultimate, or Home Premium): $4
Microsoft Office 2010 standard: $4
Microsoft Office 2010 Pro Plus: $4
Windows Small Business Server 2011 Standard 64-bit : $2
Windows Server 2008 R2 Enterprise : $2
Windows Server 2008 R2 Datacenter with SP1  : $2
Windows Server 2008 Datacenter: $2
Windows Server 2008 Enterprise: $2
Windows Server 2012 R2 Standard : $3
Windows Server 2012 R2 Datacenter : $3
Windows Server 2012 R2 Essentials: $3
Windows Server 2012 Standard : $3
Windows Server 2012 Essentials  : $3
Windows Server 2012 Datacenter : $3