To estimate a maximum purchase price for the coin in question, we will consider several factors:

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

2. Previous Prices: By observing previous auction prices for coins with similar conditions (80 and 75), we can see that they have reached hammer prices of up to 320 euros (in the case of the auction on 2022-07-07) and 270 euros (in the auction on 2023-02-28).

3. Average Hammer Price: The average hammer price for this coin is 138.67 euros, providing a baseline for the expected value.

4. Starting Price and Average Starting Price: The current starting price is 60 euros, and the average starting price is 82.1 euros. This suggests that the market is willing to accept a higher price than the starting price.

5. Sales Trends: The coin has been auctioned 20 times, of which 15 have been successful sales. This indicates a consistent interest in the coin.

Based on these factors, an estimated maximum purchase price could be in the range of 200 to 250 euros, considering that the condition is good and there are precedents of higher hammer prices in the past.

Therefore, a reasonable estimated maximum purchase price could be 250 euros.