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

1. Current starting price: 1500 euros.
2. Average auction price in the past: 1817.82 euros.
3. Auction price history:
- The coin has had auction prices ranging from 950 euros to 3400 euros, depending on its condition.
- The most recent auction prices are 2000 euros (2024-03-14) and 3101 euros (2024-05-27).

4. Condition: There is no information about the current condition of this coin, which can significantly affect its value. However, by observing the auction prices of coins with similar conditions (around 80-95), we can infer that the auction price could be in a high range.

5. Trends: The overall trend shows that auction prices have been increasing in recent years, suggesting that the demand for this coin may be growing.

Given all this, an estimated maximum purchase price could be in the range of 2000 to 2500 euros, considering that the average auction price is 1817.82 euros and that recent auction prices have exceeded 2000 euros.

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