No logic in throwing away a working drive just because its 4 years old!!
As for prices, LG DVD writer is available for 1,050 here. I bought my Moser Baer LiteOn for 1,200. That was couple weeks back.
My logic is that the drive definitely must have exceeded the warranty period now.
Also, since it is about 5 years old, it will be heavy on the pocket to fix it too.
In most cases, a new drive can be bought with better features at the same cost of repairing the old one (if not cheaper)
So, it is better to go for new a drive once you are sure the old one refuses to work despite repeated attempts (AFAIK, this is clear from the fact that even lense cleaners have no effect)
That all

PS. my 700th post