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

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 average hammer price for similar coins has been 575.38 euros.
- In previous auctions, hammer prices have varied, but there are examples of sales reaching up to 950 euros for coins with similar conditions (as seen in the March 2022 auction).

3. Starting Price and Average Starting Price:
- The current starting price is 300 euros, which is below the average starting price of 408.33 euros. This suggests that there is potential for the hammer price to be higher.

4. Sales Trends: The coin has been sold in 13 out of the last 14 auctions, indicating good demand and sustained interest in the coin.

5. Comparison with Previous Prices:
- In the most recent auction (2024), the coin sold for 550 euros with a condition of 80, setting a precedent for the current hammer price.

Based on these factors, an estimated maximum purchase price could be in the range of 600 to 750 euros, considering that the condition is good and there is a history of hammer prices supporting this estimate.

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