If the info available on the internet is accurate (the Farlux - like all other binoculars from Eschenbach - is not produced anymore), this would be a 7x42 with a rather narrow FOV (122m / 1000m), not ideal for birding (I really wonder whether that is the correct value).
There are and have been some used Farluxes advertised in the € 120 to 200 range, so €500 appear very high, even if the binocular were to be in excellent condition.
I think it is important to specify the model. Canip has located one Eschenbach Farlux 7x42 (I'd be surprised if he didn't have it in THE Pinacollection ), but I'm aware that there is at least another model sharing (partly) that name. Maybe you are talking about the Eschenbach 7x42 SPS Farlux?
If so, I've been interested in that model for quite a while, since it is a usual offer on different auction sites.
After reading many posts here and over in Cloudy Nights it seems that it is a sibling of a pretty extensive family of devices probably manufactured by the same company with very similar main specs: central dioptre setting ring, always 8º FOV, always a weight between 850 and 900 g (although most probably coatings and other specs may vary, I have no idea or experience about that). You can find it under names such as Eschenbach Farlux, Fujinon CD, Meade/Bresser Montana, Bushnell/Bausch & Lomb Discoverer, etc. Find a picture attached to see what I mean.
If you do a search here on BF under those names in 7x42, you'll be able to read many interesting threads. And if you run an image search with those names and "7x42", you'll see that the body is so similar to say the least.
I've been very tempted by one of those incarnations showing up lately on the italian Ebay, it started with a price of 250 €, but after not being sold on several occasions, the last time I checked it it was around 165 €, which I think it is a more reasonable price. I even contacted the seller and was told that it was the later phase coated version. It's here: https://www.ebay.es/itm/Binocolo-bi...472527?hash=item421db8814f:g:KykAAOSwjsxe63EX
So 500 € for a Farlux SPS seems pretty steep. In Germany I've seen them go for as little as 100something €, and usually no more than 250 €.
Do a little search among its siblings and see what you can get