I don't see that on the Amazon site. Be sure to check the model number closely as Amazon will put up other model numbers than what you searched for.
Sometimes it is just a matter of the seller trying to get rich.
I see a lot of things on Ebay these days that are far more than the price of the item in the store.
This week I bought a cordless lithium screwdriver for $17.99 at Sears. That same unit was as high as $30 on Ebay.

 

Any idea why a st 50 panny plasma is $500.00 more [ Amazon] than a st 60?

I suspect you're looking at two different sizes as opposed to the 2012 model vs the 2013 model.

Bigger TVs cost more than smaller TVs.

Looking at Vizio TVs on Amazon, the 60" Razor model is 54% more than the 50" model and the 70" Razor model is 70% more than the 60" model.

It isn't like it was back in the days of rear projection TVs where the difference was mostly plastic screen and casework.

 

No-brainer, you buy the newer model....there is a point when last years model is not cheaper anymore, considering its almost 2 years ago model, it might have something to do with it as now it gets to unscrupulous retailers price gouging on the few remaining models they have left.

 

Right, there are some industries where newer model can be a downgrade, but not here. Get the ST60.