Based on the data provided, we can observe that the coin in question has had a starting price in the current auction of 12 euros, with a conservation grade of 30 (BC+). Additionally, it has been auctioned in the past on several occasions, with closing prices ranging between 8 and 85 euros.

The average starting price of previous auctions has been 15.63 euros, while the average closing price has been 34 euros. The conservation grade of the coin in previous auctions has mostly been 70 (FDC).

Given that the estimated purchase price in the current auction is 12 euros and considering the previous closing prices as well as the conservation grade of the coin, we could estimate a maximum purchase price around 40-50 euros. It is important to note that this is just an estimate and the final price may vary depending on the demand in the current auction.