Multicast wouldn't help with the major congestion on VM's network, the connection between the uBR and the customers though.
Wholesale transit costs have gone down greatly. You can pay less than £10/Mbps/month now without buying in the sort of quantities a multi-million customer ISP would, it's not that many years ago that three times that was an excellent price. Internet bandwidth has never been cheaper.
http://www.dslreports.com/shownews/95203
£2/month per Mbps on a 10GbE port with a 3 year contract in the states. Just a Google search for transit shows under £10/Mbps/month in the UK from resellers of transit.