To estimate a maximum purchase price for the coin with a grade of 80 (MS+), we can analyze historical data from previous auctions and consider several factors:

1. Grade: A grade of 80 (MS+) is quite good, suggesting that the coin has significant value in the market.

2. Previous auction prices: By observing the hammer prices of coins with similar grades (around 80), we can see that the hammer prices have varied. For example:
- In 2018, a coin with a grade of 80 was sold for 15 euros.
- In 2019, a coin with a grade of 85 was sold for 40 euros.
- In 2020, a coin with a grade of 85 was sold for 20 euros.

3. Price trends: The average hammer price for this coin is 44.1 euros, indicating that, in general, buyers are willing to pay around this amount.

4. Average starting price: The average starting price is 31.26 euros, suggesting that sellers are starting the auctions at a reasonable price.

5. Supply and demand analysis: Given that there have been 60 auctions and 50 sales, this indicates a consistent interest in the coin, which may increase its value.

Based on these factors, an estimated maximum purchase price for the coin with a grade of 80 (MS+) could be in the range of 50 to 70 euros. This is based on the analysis of previous hammer prices and the general market trend. However, it is important to note that the final price may vary depending on the competition in the auction and the demand at that specific moment.