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

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

2. Previous Prices: By looking at the auction prices of coins with similar conditions (90-95), we can see that they have reached auction prices that vary considerably. For example:
- In 2018, a coin with a condition of 95 was auctioned for 445 euros.
- In 2022, another coin with a condition of 90 was auctioned for 400 euros.
- In 2023, a coin with a condition of 80 was auctioned for 260 euros.

3. Starting Price and Average Auction Price: The current starting price is 600 euros, and the average auction price for this coin in the past has been 210.28 euros. However, since the condition of this coin is above the average of previous auctions, it is reasonable to expect that the auction price will be higher.

4. Market Trends: Given that the coin has been auctioned 89 times and has had a high sales percentage (85 out of 89), this suggests that there is consistent interest in this coin, which may increase its value.

Based on these factors, 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 of auction prices exceeding 400 euros. However, given the starting price of 600 euros, it is possible that the auction price will approach this value, especially if there is competition among bidders.

Therefore, an estimated maximum purchase price could be 600 euros.