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

1. Current Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The coin has been auctioned 8 times and has sold on all occasions, indicating consistent demand.
- The average hammer price in the past is 320.63 euros, suggesting that buyers are willing to pay above the starting price in most cases.
- In the most recent auction (2022), the coin sold for 550 euros, indicating that, despite variability, there is potential for high prices.

3. Starting Price and Average Hammer Price:
- The current starting price is 250 euros, which is higher than the average starting price of 175 euros in previous auctions. This may indicate that the seller is confident that the coin will reach a higher price.
- Given that the average hammer price is 320.63 euros, this can serve as a benchmark for the estimated price.

4. Price Trends:
- Observing previous hammer prices, there is a trend for hammer prices to exceed the starting price, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 600 euros, considering that the last auction reached 550 euros and that the coin's condition is good. A price of 500 euros could be a reasonable target, as it falls in the middle of this range and reflects both demand and the quality of the coin.