THis banjo has been listed on our national auction site. There is nothing that suggests Gibson to me but have asked for more photos of the inside pot to be posted. Look at the stamped lettering on the rear of the peghead.
$2500 seems like a pretty steep price for this one but I don't know what banjos go for in New Zealand.
The world is full of dreamers. Also there are many people here who have no idea about banjos and thier values. This is especially true of music shops. I have seen quite a few people put banjos up for sale on the site and state that it was valued at a certain price because the music shop said it was that. There is no way the seller is going to get what he is asking. I have seen a Gibson RB 250 here sell for NZ$2000 from a music store. My estimation for this banjo is around the NZ400-600 mark.
I'm assuming that the price was given in NZ dollars. I just looked up the exchange rate, and I think NZ$2500 is about US$1800. That's still pricey for that banjo (or would be here in the States, at any rate).