I am not sure of your exact monitor
but some monitors allow you to unplug the HD15 cable from both sides and put in a new one (15-20 bucks at most).
Or if your monitor supports BNC, you could get a BNC cable which may offer better image quality anyways.
Otherwise, it might be expensive and painful to replace.
Is it going to cost as much as a new monitor? Not sure, you could always call around and get price quotes.