To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially considering the coin's condition (80, MBC+) and the hammer prices from previous auctions.

1. Condition: The coin has a condition of 80 (MBC+), indicating that it is in fairly good shape, but not the best possible condition. This suggests that its price should be below that of coins in superior conditions (such as FDC or MBC).

2. Previous hammer prices: Looking at the hammer prices of coins with similar conditions:
- In 2012, a coin with a condition of 90 was auctioned for 33,294.24 euros.
- In 2014, another coin with a condition of 90 sold for 22,748.32 euros.
- In 2016, a coin with a condition of 90 was auctioned for 5,115.16 euros, but with a condition of 30, indicating that the price can vary significantly with the condition.

3. Average hammer price: The average hammer price for this coin is 5,233.60 euros, which is also a good indicator.

4. Price trends: Given that the coin has been auctioned 19 times and sold 13 times, there is a constant interest in it. This can influence the price, as higher demand may drive up the hammer price.

Based on these factors, an estimated maximum purchase price for the coin with a condition of 80 (MBC+) could be in the range of 4,000 to 6,000 euros. This is based on the average hammer price and the condition, which is a key factor in determining value.

Therefore, a reasonable estimated maximum purchase price could be 5,500 euros.