It's not going to be worth more than 4k because that's not how you make money. There are a lot of people with a lot of NX out there, unfortunately the ones who have hoards of it tend to spend it on ridiculous stuff like clothing (which is why it costs so much; 'cause they know those people will buy it.)
For things like this it's best to price it moderately so no one is turned off by it. 100 hammer's at 4k is $400 for them, where if they price it at say 8k or 10k a lot less people will be willing to shell that much out, and definitely not repeatedly, so they'd be lucky to see even a quarter of the overall sales. Since they have no limit in their stock it would be silly and a grave mistake for them to overprice it.
For things like this it's best to price it moderately so no one is turned off by it. 100 hammer's at 4k is $400 for them, where if they price it at say 8k or 10k a lot less people will be willing to shell that much out, and definitely not repeatedly, so they'd be lucky to see even a quarter of the overall sales. Since they have no limit in their stock it would be silly and a grave mistake for them to overprice it.