I agree that you will have a very difficult time getting €329 for a used FP2 with a broken cover. Besides trying to get people to pay a premium price for an unrefurbished, damaged device with no full warranty, even if it were ship shape it’d be an old phone that’s not really in demand anymore.
Depreciation is the name of the game when talking about consumer electronics. In 2011, I paid €400 for a Sony Xperia Z1 Compact - today, I can go on eBay and buy one for €40 (or less, if I keep an eye out for a little while). Likewise, at this point the FP2 just isn’t in demand anymore except with enthusiasts - and enthusiasts don’t pay top dollar.
This is evidenced by the fact that there’s an FP2 being sold right now on this forum, same as yours but with an extra battery and no aesthetic defects for £200 including postage, and another with a spare third party battery for €150, and yet another one with the old camera modules for £100. For the price you’re asking, someone could buy two or three functioning FP2s in equal or better shape.