Based on the provided data, we can observe that the coin in question had an opening price of 12 euros in this auction, with a grade of 30 (BC+). In previous auctions, opening prices have ranged from 1 to 40 euros, with estimated prices between 15 and 60 euros, and final prices between 18 and 40 euros.

The average opening price of this coin in previous auctions has been 19.17 euros, while the average final price has been 27.67 euros.

Given that the current grade of the coin is 30 (BC+), and considering the prices from previous auctions, we could estimate a maximum purchase price of around 25-30 euros for this coin in the current auction. It is important to note that factors such as demand at the time of the auction and the availability of interested buyers can influence the final selling price.