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

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

2. Previous Prices: By looking at previous auction prices for coins with a similar condition (80), we can see that they have reached auction prices of up to 370 euros (in the March 2020 auction) and 360 euros (in the June 2022 auction). This suggests that the market is willing to pay significant prices for coins in this condition.

3. Average Auction Price: The average auction price for this coin is 269.3 euros, providing a solid basis for estimating the maximum price.

4. Starting Price: The current starting price is 250 euros. This may influence bidder behavior, as a lower starting price can attract more interest.

5. Recent Trends: In the most recent auctions, the hammer prices have been quite high, suggesting a positive trend in interest for this coin.

Taking all these factors into account, an estimated maximum purchase price could be around 370-400 euros. This range is based on previous auction prices for coins of similar condition and the current market trend. However, it is important to remember that the final price may vary depending on competition in the auction and other market factors at the time of the auction.