Based on the provided data, we can see that the coin in question has had a starting price in the current auction of 18 euros and is in a conservation grade of 30 (BC+). Additionally, it has been auctioned in the past on several occasions, with closing prices ranging between 15 and 50 euros.

The average closing price of this coin in the past has been 152.91 euros, with an average starting price of 61.85 euros. Considering that the coin is in a conservation grade of 30 (BC+), we can estimate that its closing price in this current auction could be in a similar range to previous auctions.

Given that the coin has sold in the past in a price range between 15 and 50 euros, and considering that the average closing price has been 152.91 euros, we could estimate a maximum purchase price in this current auction around 50-60 euros.

It is important to note that the final auction price will depend on several factors, such as the demand from buyers present at the auction, competition from other bidders, and the specific condition of this coin compared to previous ones auctioned.