Based on the provided data, the coin in question has a starting price of 18 euros and has been auctioned twice in the past, both times sold. The coin's condition is graded as 25 (BC). In the last recorded auction, which took place on November 19, 2020, the coin had a starting price of 18 euros, an estimated price of 30 euros, and a final price of 60 euros, with a condition value of 30.

Considering that the average final auction price of this coin is 52.5 euros and that in the last auction the final price was 60 euros, we can see that the coin has increased in value. Given that the coin's condition is 25 (BC), which is below the average condition, and taking into account the increase in the final auction price in the last auction, we could estimate a maximum purchase price of around 65-70 euros for this coin in the next auction. It is important to note that this is just an estimate and the final price may vary depending on various factors in the auction.