Microsoft Office 2011

I bought the home user version it in January 11. I have just upgraded my iMac andam being told I am unable to transfer ther software to my new machine unless I pay approx. £90 odd for another license. They say they do not offer an option of deleting the software from my old machine and activtaing it on the new. Can this be true? It does not apply to any other softare I use?. If this is the case they need to make it clearer at the time of purchase. I can now see how the language used can be interpreted in that way but it seems a very unreasonable approach. If true I will manage without .