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

1. Condition of the coin: The coin has a condition rating of 85 (ebc-), indicating that it is in quite good shape. This is relevant because coins in better condition tend to fetch higher prices at auctions.

2. Previous auction prices:
- The average hammer price for this coin in the past is 2818.18 euros.
- Previous hammer prices have varied, but there are examples of auctions that have reached up to 6500 euros in exceptional conditions (such as the 2019 auction with a condition rating of 95).

3. Current starting price: The starting price is 2500 euros, which is a reasonable starting point.

4. Price trends: Looking at previous hammer prices, it seems that most coins with a similar condition (85) have reached hammer prices around 2000 to 2600 euros, although there are exceptions that have exceeded 3000 euros.

5. Estimation: Given that the condition of this coin is 85 and considering the average hammer price and previous auction prices, an estimated maximum purchase price could be between 3000 and 3500 euros. This is based on the fact that, although the starting price is 2500 euros, the price trend and condition suggest it could reach a higher price.

Therefore, an estimated maximum purchase price for this coin could be 3500 euros.