Can you price this magical item, please?

[Jon_Dahl]

Medallion of Foil See Invisibility

This appears to be a very small pendant disk hung from a fairly long neck chain. Usually fashioned from bronze, copper, or nickel-silver, the medallion allows the wearer to remain unseen when looked upon by someone under the effect of See Invisibility spell.

Faint abjuration; CL ?; Craft Wondrous Item, ?; Price ? gp.

[Biggus]

As far as I can see, the nearest thing to the effect you want would be a continuous item of Lesser Spell Immunity (SpC). It doesn't actually work with See Invisibility, but it should give a guideline as to what something which protects against a single spell should cost. It would come out to 18,000GPs in this case, you might want to adjust it a little but it at least gives a place to start from.

[Tzardok]

I would start from Nondetection. It doesn't do this effect usually, but it's closest conceptually.

[Biggus]

I would start from Nondetection. It doesn't do this effect usually, but it's closest conceptually.

I can see your thinking, but if you're going that way Invisibility itself seems closer. Also, Nondetection allows a caster level check to overcome it, this doesn't.

@OP: Ring of the Darkhidden (MIC p.122) might be another point of comparison, it stops a form of special sight and is only 2,000GPs.