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

1. Current condition: The coin has a condition of 85 (MBC+/EBC-), indicating that it is in quite good shape. This suggests that its value could be in the upper range of previous auctions.

2. Previous auction prices: By observing the hammer prices of coins with a similar condition (85), we can see that they have reached hammer prices ranging from 2,800 to 5,500 euros in previous auctions. For example:
- In 2019, a coin with a condition of 85 was sold for 2,800 euros.
- In 2023, a coin with the same condition was sold for 5,500 euros.

3. Average hammer price: The average hammer price for this coin is 3,169.5 euros, which is also a good indicator of the expected value.

4. Starting price: The starting price is 2,500 euros, which is reasonable and aligns with previous starting prices.

5. Price trends: In recent auctions, hammer prices have shown an upward trend, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price could be in the range of 4,000 to 5,500 euros, considering that the condition is good and there is a trend of increasing hammer prices.

Therefore, a reasonable maximum purchase price could be 5,000 euros.