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

1. Coin Condition: The coin to be auctioned has a condition of 85 (ebc-), indicating that it is in quite good shape. This is important because coins in better condition tend to fetch higher prices.

2. Auction History:
- It has been auctioned 9 times in the past, of which it has sold 8 times. This indicates good demand.
- The average hammer price in previous auctions is 487.14 euros, which can serve as a reference.

3. Previous Auction Prices:
- In the March 2022 auction, a coin with the same condition (85) sold for 750 euros, which is the highest recorded price.
- In other auctions, prices have varied, but the range seems to be between 250 and 750 euros, depending on the condition and demand at that time.

4. Starting Price: The starting price of 600 euros is a good indicator of what is expected to be obtained for the coin, but it does not necessarily reflect the final hammer price.

Based on these factors, an estimated maximum purchase price could be in the range of 700 to 800 euros, considering that the condition is good and there have been precedents of sales at higher prices. However, since the starting price is 600 euros, it is likely that the final hammer price will be closer to that value unless there is significant competition among bidders.

Therefore, a reasonable maximum purchase price could be 750 euros.