To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition of 75 (MBC), indicating that it is in fairly good shape, but not the best possible condition.

2. Previous Auction Prices: By looking at the auction prices of coins with similar conditions (75 and 80), we can see that:
- In previous auctions, coins with a condition of 75 have reached hammer prices of up to 120 euros (as in the auction on 2017-10-19).
- Coins with a condition of 80 have reached hammer prices of up to 80 euros (as in the auction on 2022-02-22).

3. Average Hammer Price: The average hammer price for this coin is 39.46 euros, giving us an idea of its usual market value.

4. Estimated Price: The estimated price for the current auction is 15 euros, which is quite low compared to previous hammer prices.

5. Trends: Since the coin has been auctioned 36 times and sold 32 times, there is good demand for this coin, which may influence the price.

Based on these points, an estimated maximum purchase price could be between 70 and 90 euros, considering that the condition is 75 and there have been previous auctions in that range. However, since the starting price is 15 euros, it is likely that the hammer price will not reach the maximum, but it could be in the mentioned range if there is sufficient interest in the auction.

Therefore, a reasonable maximum purchase price could be 80 euros.