Based on the provided data, 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 varying starting and final prices.

The average starting price of this coin in previous auctions has been 40.67 euros, while the average final price has been 74.22 euros. We can also see that it has had different estimated prices in previous auctions, with conservation grades ranging between 75 and 80.

Given that the current starting price is 12 euros and considering the previous prices of this coin, as well as its conservation grade, we could estimate a maximum purchase price around 70-80 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.