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

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

2. Previous Prices: By looking at previous auction prices for coins with similar conditions (75 and 80), we can see that auction prices have varied. For example:
- In 2022, a coin with a condition of 75 was auctioned for 40 euros.
- In 2023, it was auctioned for 35 euros.

3. Average Auction Price: The average auction price for this coin is 36.09 euros, which gives us a good reference.

4. Starting Price and Average Starting Price: The current starting price is 25 euros, and the average starting price is 30.47 euros.

5. Recent Trends: In the most recent auctions, the auction prices have ranged from 25 to 40 euros for similar conditions.

Based on this data, an estimated maximum purchase price could be in the range of 40 to 50 euros, considering that the coin is in good condition and that previous auction prices have reached up to 40 euros under similar conditions.

Therefore, a reasonable maximum purchase price could be 45 euros.