If you wanted to upgrade the controller to the USB version, then it's over £1k, but the software license alone isn't that much.

A Novamill more than capable of handling steel. The biggest issue is it's not got that powerful a motor, so you have to make sure you use suitable cut rates. I'm sure I did work out a bigger servo motor could be squeezed in, but I really needed a bigger work area, so I bought a Triac and sold my Novamill.