OP,
i can advise you to be very careful when purchasing products online with significantly very low pricing compare to MSRP(manufacturer Suggested retail Pricing).
Big online Retailers like amazon etc can do that because they usually get very low pricing from manufacturers as they are bulk purchasers.But even Amazon won't do that just to have low pricing,they are a business and the only time they will sell products below MSRP is when the product is nearing it's product circle and they have to clear they warehouses for new products.
Regarding what you saw at ALIBABA.i can only say IT"S TOO GOOD TO BE TRUE,LED Televisions are very expensive,more so than plasma and LCD,for $550 it's even difficult to get an LCD TV with 55",how can you get an LED TV for that pricing,that is beyond cheap.
Lemons are always going to be Lemons no matter how Sweet,they are,they will never turn into Oranges.The call is yours although,go ahead and jump into that deep water hole,when you get back we will be here with a shoulder to cry on.
Outside advise,if you are looking for a TV check their company website,Be it Sony,LG,Samsung etc,usually they have MSRP,this will give you a clue,anything less than 30% of MSRP should raise Bells and Whistles.