Brendan, the valuation of €80k is simply the book value of the assets. If you look at the adjustments referred to in the OP, it appears the debtors, fixed assets and stock are all worth less than book value - apparently to the tune of ~50k which reduces the net asset value to 30k.
The OPs share is half of this, but since it isn't a majority share, it is reduced (by 30%), to 11.5k.
So as long as the adjustments to stock, fixed assets and debtors are correct, then the valuation may be reasonable, and liquidating, with the associated costs, will not exceed this.
Unless of course there is Goodwill to be factored in (unlikely since the business is only treading water).