Based on the data provided, we can observe that the coin in question has had varying starting and final prices in previous auctions. The current condition of the coin is 25 (BC), indicating that it is not in the best condition.

The starting price for the upcoming auction is 18 euros, with a historical average starting price of 65.33 euros, and a historical average final price of 97.86 euros.

Considering that the coin has been sold in the past in a price range from 25 euros to 170 euros, and that the current condition is 25 (BC), we could estimate a maximum purchase price around 60-70 euros, taking into account that the coin is not in the best condition and that the starting price is relatively low compared to historical final prices.

It is important to note that the final auction price will depend on the demand from buyers at that specific moment, so it is advisable to monitor the auction's progress to adjust the offer accordingly.