To estimate a maximum purchase price for the coin in question, we can consider several factors:

1. Coin Condition: The coin to be auctioned has a condition of 80 (MBC+), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History: By observing the hammer prices of coins with similar conditions in the past, we can see that:
- Coins with a condition of 80 have reached hammer prices of up to 95 euros (as seen in the auction on January 31, 2023).
- Coins with a condition of 90 have reached hammer prices of up to 170 euros (as seen in the auction on December 11, 2024), indicating that there is a market willing to pay high prices for well-preserved coins.

3. Average Hammer Price: The average hammer price for this coin is 76.12 euros, which can also serve as a reference.

4. Starting Price: The starting price is 40 euros, which is relatively low compared to previous hammer prices.

Taking these factors into account, an estimated maximum purchase price for the coin could be in the range of 90 to 110 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 100 euros.