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

1. Condition: The coin has a condition of 95 (EBC+), indicating that it is in very good shape. This generally increases its value compared to coins with lower conditions.

2. Previous auction prices:
- In 2021, a coin with a condition of 95 sold for 5000 euros.
- In 2022, a coin with a condition of 90 sold for 5000 euros, suggesting that condition has a significant impact on price.
- In 2024, another coin with a condition of 95 sold for 5400 euros.

3. Starting price and average hammer price: The current starting price is 4000 euros, and the average hammer price in previous auctions is 3810 euros. This suggests that the starting price is reasonable and that there is potential for the hammer price to be higher.

4. Auction trends: Since the coin has sold every time it has been auctioned, this indicates a consistent interest in the coin, which may lead to an increase in the hammer price.

Based on these factors, an estimated maximum purchase price could be between 5000 and 6000 euros, considering that the condition is high and that previous hammer prices for similar coins have been in that range. A price of 5500 euros could be a reasonable target, given the sales history and the condition of the coin.