I read your words very carefully and the original poster stated quite clearly that the TV was not for their personal use and they were bringing it down to resell to their friend. They had already made up their mind. Your alternative suggestion as to why they would be bringing it down is not the truth in this situation. To suggest they use it amounts to asking them to lie to the Jamaican government.
Please dont think that the customs agents are not aware of the various scams that visitors, expats and even returning Jamaicans try to use to justify their intention to get around the laws. They are fully aware of them and have ways to deal with them. In this case, should they not believe the "tv for my own personal use in a room with no tv" scenario, they will often make the visitor pay duty on the tv, then ask them to keep the receipt and present it when they return to customs WITH the tv for a refund. If the visitor claims they decided to leave it behind or claims it was "stolen", then no refund is given.
As for the TVs available on the island, I would check Courts, Mega Mart and ATL once you are on the island - all are on the way to Negril from the Montego Bay airport. Not all their products are on their websites. They always have other items in stock that they do not mention on the internet. We saw several new flat screenTVs under $200us in the stores just last week - and none are listed on the websites.
As pointed out by RockRobster, bringing in a new tv for your home here in Negril is exactly why duty is charged on items. To get a duty free exemption you would have to fill out more government forms and show proof of property ownership, your government issued TRN as well as all the receipts for the various items you are bringing in. And please note, if you do plan to live in another country, it is always wise to actively support the economy of that country. It will be to your future benefit to help the economy grow.