That's not right in my opinion as i had to send 2 LE40B650 tv's back to Amazon at NO extra cost to me as they were faulty!! It may be the policy of your retailer to charge for returns but i'm sure if you fight this given the other info provided above by Electroman you may well get a result. Both the TV's i sent back were at most 6days old and the 2nd one went back the next day it was that bad and i wasn't charged for either return.
Just out of interest what is wrong with your TV? My first LE40B650 had severe clouding in the top 2 corners of the screen and the 2nd one had several pixels that were always lit ie: always bright white. I gave up in the end and went for a Sony 40W5500 instead and even then i had to take the first one back with severe clouding again, the replacement is excellent however!