To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition of 80 (MBC+), indicating that it is in quite good shape.

2. Previous Auction Prices:
- In previous auctions, coins with a similar condition (80) have had varying hammer prices, but we can observe that the average hammer price for coins with a condition of 80 has been approximately 37.25 euros.
- There are also specific examples of previous auctions:
- 50 euros in October 2019.
- 31 euros in July 2020.
- 45 euros in July 2019.
- 50 euros in February 2022.

3. Starting Price: The current starting price is 25 euros, which is reasonable given the price history.

4. Trends: In recent auctions, hammer prices have shown a trend of increasing, especially for coins in good condition.

Based on this data, an estimated maximum purchase price could be in the range of 50 to 70 euros, considering that the highest hammer price for a coin in similar condition has been 50 euros and that the market may be willing to pay more for a coin in good shape.

Therefore, a reasonable maximum purchase price could be 65 euros.