France ,30 C Napoleon III. Imperforated Essay Sheet -Is The Price Correct?

Could you please comment the this sheet of 30 C Napoleon III. Imperforated ESSAY stamps. The price asked for it is ,much higher than the catalog value . The German seller points the fact that it is a full sheet not a single or pair of stamps. This is used as a argument for the substantial price asked for it .

Here is a link to it :
https://www.kleinanzeigen.de/s-anze...185-234-3371

That seems highly inflated. On Delcampe, I can find a sheet of 90 for 910 Euros. There would be a premium for a full sheet, but nowhere near that IMO.

It is a sheet of 150 printed on both sides.
Also, the seller writes it "was very expensive, so no non-serious offers."

Sounds like someone is trying to recover what he paid, maybe with a decent profit margin.

Ah, I missed the printed on both sides part. Interesting.

You can ASK whatever you like. Intact sheets and panes that have survived this long are generally scarce or rare birds. The printing on both sides says "printers waste" to me.

The description says "Probedruck" which is a printer's proof. It may come from a printer's archive or from printer's waste.

I wasn't paying attention when I posted my question. I couldn't say that a full sheet of printed on both sides stamps is not a rare find . I also tough it could be a printers waste sheet, but the reason to ask was , the price which looked me much higher than the usual one on which such essay stamps were offered at the market.
Of course a collector could sell this or other object at a price which decides is the most appropriate.