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

1. Current Condition: The coin has a condition of 85 (ebc-), which indicates that it is in quite good shape. This is important because coins in better condition tend to reach higher prices.

2. Historical Prices: By looking at previous auction prices for coins with a similar condition (85), we can see that they have reached varying auction prices. For example:
- In the auction on 2023-02-16, a coin with a condition of 85 sold for 2000 euros.
- In the auction on 2023-12-13, another coin with a condition of 85 sold for 2600 euros.

3. Average Auction Price: The average auction price for this coin is 2749.1 euros, which also gives us an idea of the market value.

4. Starting Price and Average Starting Price: The current starting price is 1500 euros, and the average starting price in previous auctions is 1620.69 euros. This suggests that the starting price is reasonable compared to the history.

5. Market Trends: Since the coin has been auctioned 33 times and has had a sell-through rate of 90.9% (30 out of 33), this indicates a consistent interest in this coin.

Based on these factors, an estimated maximum purchase price could be between 2500 and 3000 euros, considering that the highest auction price for a coin with a similar condition was 2600 euros and that the average auction price is 2749.1 euros.

Therefore, a reasonable maximum purchase price could be approximately 2800 euros.