"About 6 months later the left side of the screen appeared darker than the other."
This is caused by a problem with the LG display panel. Specifically: there is a tiny plug that is loose.
When Apple do fix this problem, they simply replace the whole screen.
It is possible (although difficult) to simply fix the plug itself, as explained at length on this site by many people. There are now one or two workshops around the world that will fix the plug, it is such a common problem.
"they told me Apple's warranty would not cover this problem"
That is incrdeibly bizarre. If your computer was under 12 months old, all you had to do was walk in to any Apple shop with the machine, and Apple would have fixed it. (ie, they simply swap the screen.) They do this for many people, naturally - it's under warranty. You could probably still do this, if it's less than 12 months old!
Further, if you had Apple's extended three year warranty, again they would just replace the screen. Again this happens all the time since it's such a common problem.
The reason everyoneis hating on Apple over this issue - since it is an absolutely well-known problem affecting vast numbers of people, Apple should recall all the screens and fix them, ie, they should fix them even IF the warranty is expired.
(Of course, obviously, if still under warranty they fix it - they just swap the screen.)
"The repair of this problem (about $1,700 dollars)"
That is bizarre. It's not THAT expensive. If you take one of these in to Apple and ask them to simply replace the screen, it is about 1000 bucks (it varies by country etc).
I'm really sorry you goty ripped off so badly by BestBuy. It's weird because they sort of "ripped off themselves" - they could have easily simply swapped the screen at a parts cost of 700? or so bucks.
I would never, ever, ever buy those warranties which large retailers offer - they're always a ripoff. You could have bought the actual Apple extended warranty.
Also again absolutely bizarrely - if your machine was under 12 months, you could have just walked in to any Apple shop or phoned them and they would have swapped for a new screen in a couple days. Really sorry to hear your story.
Regarding refurb macs, yes simply click to apple.com and there is a huge selection.