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

1. Condition of the coin: The coin to be auctioned has a condition of 95 (EBC+), which indicates that it is in very good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous auction prices: By observing the hammer prices of coins with similar conditions (around 85-95), we can see that the hammer prices have varied. For example:
- A coin with a condition of 95 was auctioned for a hammer price of 350 euros.
- Another with a condition of 85 sold for 200 euros.

3. Average hammer price: The average hammer price for this coin is 114.02 euros, but given that the condition is higher, we can expect the hammer price to be higher.

4. Starting price: The starting price is 400 euros, indicating that the seller expects a considerably high price.

5. Auction trends: The coin has been auctioned 63 times, of which 57 have been sold. This suggests that there is a consistent interest in this coin.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 400 to 600 euros, considering that the condition is high and there are precedents for hammer prices in that range. However, given the starting price of 400 euros, it is likely that the hammer price will not significantly exceed this value unless there is active competition among bidders.

Therefore, an estimated maximum purchase price could be 550 euros.