Based on the data provided, we can observe that the coin in question has had an average auction closing price of 25.57 euros in previous auctions. Additionally, its condition has been maintained at a level of 80 (MBC+).

Considering that the starting price for the next auction is 12 euros and that the historical average starting price has been 20.54 euros, we could estimate that the closing price could be around 25 euros, which is the historical average closing price.

Given that the condition of the coin remains at a high level (80), and considering that in previous auctions it has reached closing prices above 25 euros, we could consider a maximum estimated purchase price of around 30 euros for this coin in the next auction.