"retails at US$1,295." I'm not sure if it actually does upscaling, if it doesn't your still stuck with the scaler in your plasma or you could use it to hook up your Dual Link HD-SDI modified blue ray disc player!
Thought I'd give you another 'option' if you are looking for SDI to DVI adapters - the Gefen 2:1 has a UK price nearer the £650 (ex vat) mark; though it lacks the audio delay of the Black Magic HDLink.
If you need SDI to DVI with scaling then one of the NEW Lumagen 'Next Generation' scalers with SDI inputs is another possibility - you can add SDI inputs to all three of the NEW Lumagen units for £250 (though this price is only applicable for factory fitted mods installed before the units are shipped from the US).