Folding Bikes - Help on folding bike price (breezer zag 8)

My friend who knows nothing about bicycles asked me to tune up her folding bike for her so she could sell it, and she wanted me to suggest a price but I really don't know folding bikes at all so I figured I would get some advice from the experts.
The bike is a Breezer Zag 8, heres the stock specs (http://www.breezerbikes.com/index.php/component/content/article/36-bicycles/72-zag-8.html)
The bikes is mostly stock except it has a Biologic saddle (big and cushy but I don't know the model) and it has a truvativ touro crankset with no folding pedals, Sorry no pictures but I can't find a single scratch on the thing, it wasn't ridden much.
How much would you pay for one of these?
all the components are in good to great condition except the headset which seems pretty sticky but Its not noticeable when your riding.

Thanks alot sorry to bother yall but I don't want to rip anyone off, and I certainly don't want my friend to get ripped off (shes the kind of person thats prone to getting ripped off)

I'm pretty sure it's a rebadged Dahon or uses Dahon Licensed Tech. I would basically expect to get half of retail for it. MSRP is around $650.

That doesn't mean that your friend can't get more for it, but I wouldn't expect much more than half retail.

Thanks!
I wasn't comforatable telling her anything over 200 without asking around.

The bike is essentially a rebranded Dahon as Lalato mentions. The frame is a Vitesse, component spec is just like what you'd find on a Dahon Speed P8 or Mu P8. The bike is pretty much a "Vitesse P8".

The bike retails between about $600 for an older model, to $710 for the current year, I believe. I think that as long as the headset is not terminal, I would agree with Lalato's assessment and $300-350 would be pretty reasonable.