Based on the data provided, we can observe that the coin has had an average auction closing price of 87.67 euros in previous auctions. Additionally, the condition of this coin is rated at 25 (BC).

Considering that the coin will be auctioned in the upcoming days with a starting price of 9 euros, we can estimate a maximum purchase price based on the previous average closing price and the current condition. Given that the coin's condition is relatively low (25), it is likely that its closing price will not reach the historical average.

Therefore, my estimate for the maximum purchase price of this coin in the next auction would be around 70-75 euros, taking into account the condition and previous closing prices. It is important to note that this is just an estimation and the final price may vary depending on the demand at the auction.