I don't think there are any Ibanez Les Pauls worth well over $1000 US (with the exception of the Custom Agents) and the reason is simple: while nice guitars, they aren't as nice as a real Les Paul. I side by sided them back in the late 70's when I played LP Customs, and the Gibsons were nicer by a lot. That's not true of the jazz boxes though, where the Ibanezes are usually as good or better than the Gibsons (my main guitar now is a '78 Ibanez 175 copy). The Les Pauls are another story though.
If the Ibanez is a Les Paul Custom copy, in great original shape and with a set neck, it should be worth at least 400 EUR with a hard case. The original pickups were great, so you don't need to change them either. If the guitar has a bolt on neck, you can likely do better value wise with a new Tokai LoveRock for the same money, and the Tokai would have a better feeling heel joint, also. Another completely different thing to consider is a late 70's Artist if you can find one. They are for the most part as nice or nicer than period Les Pauls, and what I eventually switched to in 1980.