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A major obstacle for widespread adoption of LED sets is however the price premium, which can be as much as $700 over a traditional LCD model of the same size.

I feel strange about the usage of premium in this sentence, using "... is however the price" is enough, I guess. What can you say about this? Thanks.
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"price premium" sounds fine to me. It emphasises that the price is higher than that of other models, not just high in absolute terms. However, the sentence goes on to say as much (and as much could be guessed anyway), so "premium" can be omitted with little change in meaning.
Comments  
A major obstacle for widespread adoption of LED sets is however the price premium, which can be as much as $700 over a traditional LCD model of the same size.

Omit the word "however" and the sentence is OK. If this is in context and you are saying they are good but this is what is keeping them from being adopted. Then it should be:

However, a major obstacle for widespread adoption of LED sets is the price premium, which can be as much as $700 over a traditional LCD model of the same size.