To estimate a maximum purchase price for the coin in question, let's consider several factors:

1. Starting Price: 600 euros. This is the initial price set for the auction.
2. Auction History: The coin has been auctioned 2 times previously, and on both occasions, it was sold. This indicates interest in the coin.
3. Previous Prices:
- In 2015, the coin was auctioned with a starting price of 175 euros and sold for 900 euros, indicating high interest and possible overvaluation at that time.
- In 2020, the starting price was 20 euros, but the final bid was only 25 euros, suggesting low interest.
- In 2024, the starting price is 110 euros, with an estimated price of 200 euros, but it has not yet been sold.

4. Condition: The coin has a condition rating of 70 (MBC-), which is a positive factor, as coins in better condition tend to reach higher prices.

5. Average Final Price: The average final price in the past has been 462.5 euros, which can serve as a reference for the maximum price.

Given that the starting price is 600 euros and considering the auction history, a reasonable maximum purchase price could be in the range of 600 to 900 euros, depending on the interest of bidders in the current auction.

However, since the starting price is 600 euros and the average final price in the past is 462.5 euros, an estimated maximum purchase price could be approximately 700-800 euros. This allows for some competition in the auction but also takes into account the price history and the condition of the coin.