He will lose it. Nobody will give you 1K for 6$ only. Don't trust them. If some how 1K people try it then want happen ? They will gain 6k USD. 6K isn't small amount by the way.
I mean there is no reason to quit this anyway, because he already gamble his money, just spend $6 to get the rest of his winning does not to be bad idea since. No matter what they get as long as they are paying back his $1k so be it. What my point is, he already spend some to get his profit right now, spend some more just in case they paying do not give a big deal anyway. If they paying then good, but if they are not paying then stay away from it
As I understand he did not gamble his money, he used no deposit bonus money only. Indeed spending $6 wont be bad idea if we are talking about legit site, but here it is not really clear whether the site is legit or not. Blindly deposit to get the money he won from the no deposit bonus would be bad idea in this case. Dont suggest him something that may make he lose his money, unless you know how reliable the site is.
Update: The site is no longer available..
It was actually around 60$ not $6 even though, it's not big deal when talking about 1000$ prize but, they said the site started in 2013 and there was no reviews or nothing about them on the internet. The domain was only 8 days old. I think they succeed in making few people believe them because the 1000$ was not free offer they made us to bet on their game with the bonus money and purposefully made us win. So, they can trick us to deposit for the withdrawal. They had about 200 online players average all the time and most of them are bots and accounts made by site admins. They pretended to be players and was very active in the online chat even responded to the "real" player's doubts.