Not sure if this should go here or in monitors, so feel free to move if necessary 
I have a new machine with VGA and DisplayPort connectors, and my monitor has both VGA and DVI in. Obviously I'd rather use the DVI, which would require a DisplayPort->DVI adapter, which I believe shouldn't degrade image quality, but I was wondering if anyone knew if:
a) All these things are created equal
b) If I'm likely to be able to get one on the high street
c) Why they seem to cost £20-£50
Any advice from anyone that's running one of these adapters would be much appreciated.

I have a new machine with VGA and DisplayPort connectors, and my monitor has both VGA and DVI in. Obviously I'd rather use the DVI, which would require a DisplayPort->DVI adapter, which I believe shouldn't degrade image quality, but I was wondering if anyone knew if:
a) All these things are created equal
b) If I'm likely to be able to get one on the high street
c) Why they seem to cost £20-£50

Any advice from anyone that's running one of these adapters would be much appreciated.