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

1. Coin Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in relatively good shape. This suggests that its value should be above that of coins with lower conditions.

2. Previous Auction Prices: By observing the hammer prices of coins with similar conditions (around 80), we can see that the hammer prices have varied. For example:
- In 2022, a coin with a condition of 80 was sold for 200 euros.
- In 2023, another coin with a condition of 80 was also sold for 200 euros.

3. Average Hammer Price: The average hammer price for this coin is 233.42 euros, indicating that, in general, coins of this reference tend to reach higher prices.

4. Average Starting Price: The average starting price is 138.45 euros, suggesting that starting prices are usually lower than hammer prices.

5. Auction Trends: Given that there have been 58 auctions for this coin and 51 have resulted in sales, there is good demand for this coin, which may increase its value.

Based on these factors, an estimated maximum purchase price for the coin in question could be in the range of 200 to 300 euros, considering that the highest hammer price in the past for a coin of similar condition was 300 euros.

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