Why would someone want to buy the Halo3:Multiplayer Disc if they have no XboxLive?
It's absolutely pointless, unless you're just going to sit around in Forge all day on your own.
It's a multiplayer game, if you can't play it multiplayer, why bother paying for it? Unless you frequently have people who come around and play on the same console or system-link, it seems a waste for someone to buy it.
Personally, I'd keep it if you're the sort of person who plays Online on Halo3.
However, if you're not interested in it, then there's no reason to keep it hanging around.
$400 = £251.73. That's a fair amount and enough surely to buy the actual map packs on XboxLive and for less. I'd say, if you do sell it and are interested in the map packs, buy the actual maps from online and make some money, that is of course, if you have the original Halo3 itself, which if you don't, you'd have to buy to play it online.
Edit: And Thorax is right. All copies of Halo3:ODST come with the Multiplayer disc which as you know has all the released map packs. You can buy that for the cheap $30 or whatever your local shops sell it for. The multiplayer disc is worth much, much less than $400. You'd be a fool to pay that for it.
If you are going to accept his deal, use the money to buy another copy for a much cheaper price and treat yourself to something nice with the extra sum of money you just got.
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