To estimate a maximum purchase price for the coin in question, we can analyze the provided data:

1. Current Grade: The coin has a grade of 75 (MS), indicating that it is in an acceptable condition, but not among the best.

2. Previous Auction Prices:
- Hammer prices have varied, but generally, the hammer prices for coins with similar grades have ranged from 1800 to 3200 euros.
- The last auction with a grade of 75 had a hammer price of 2200 euros.

3. Average Hammer Price: The average hammer price for this coin is 2199.23 euros, suggesting that this is a good reference point.

4. Starting Price: The current starting price is 1600 euros, which is below the average hammer price.

5. Price Trends: Looking at previous auctions, it seems that coins with grades of 75 have had hammer prices that can exceed the starting price, especially if there is interest in the coin.

Based on these factors, an estimated maximum purchase price could be around 2200-2500 euros, considering that the average hammer price is approximately 2200 euros and that the grade is an important factor in determining value.

Therefore, a reasonable maximum purchase price could be 2500 euros.