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

1. Coin Condition: The coin has a condition rating of 75 (MBC), indicating that it is in relatively good shape, but not of the highest quality (FDC).

2. Previous Prices: By looking at the auction prices of coins with similar conditions (around 70-80), we can see that the auction prices have varied. For example:
- In previous auctions, coins with a condition of 70 have reached hammer prices of 35 euros.
- Coins with a condition of 80 have reached hammer prices of up to 90 euros.

3. Average Hammer Price: The average hammer price for this coin is 82.69 euros, suggesting that, in general, buyers are willing to pay close to this amount.

4. Starting Price: The starting price is 25 euros, which is quite low compared to previous hammer prices.

5. Auction Trends: Given that the coin has been auctioned 142 times and has had a good sales percentage (113 out of 142), this indicates a consistent interest in this coin.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 70 to 90 euros, considering that the condition is 75 and the average hammer price is 82.69 euros.

Therefore, a reasonable estimated maximum purchase price could be 85 euros.