Can anyone help solve an argument i am having with a friend - if DVD can be up scaled to 1080P - why do you need to spend £100's on expensive Blu-Ray Players - if some much cheaper DVD Player improve the quality to 1080p

Is the quality much better on Blu-Ray movies or is it just the same as an up-scaled DVD

Or am i not getting the whole 1080P resolution thing - and what this exactly means with upscaling and Blu-Ray Movies