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

1. Current Condition: The coin has a condition of 75 (MS), 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 previous hammer prices for coins with similar conditions (75-80), we can see that the hammer prices have varied. For example:
- In recent auctions, coins with a condition of 80 have reached hammer prices of up to 160 euros.
- Coins with a condition of 75 have had hammer prices ranging between 30 and 70 euros.

3. Average Hammer Price: The average hammer price for this coin is 73.76 euros, which provides a good reference point.

4. Recent Trends: In the most recent auctions, the hammer price has shown a trend of increasing, especially for coins in good condition.

5. Starting Price and Average Starting Price: The starting price is 25 euros, and the average starting price is 40.68 euros. This suggests that the hammer price could be significantly higher than the starting price.

Based on these factors, an estimated maximum purchase price for the coin in question could be between 80 and 120 euros, considering that the condition is good and there is an upward trend in hammer prices for similar coins.

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