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

1. Current 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. Historical Prices: By looking at previous auction prices for coins with similar conditions, we can see that there is a great deal of variability. For example:
- In 2011, a coin with a condition of 75 was auctioned for 5200 euros.
- In 2012, a coin with a condition of 90 sold for 60000 euros, indicating that coins in better condition can reach significantly higher prices.
- In 2016, a coin with a condition of 75 sold for 6500 euros.

3. Average Auction Price: The average auction price for this coin is 7523.26 euros, which is also an important indicator.

4. Starting Price: The current starting price is 1200 euros, which is quite low compared to previous auction prices.

5. Sales Trends: The coin has been auctioned 25 times, of which 22 have been successful sales. This suggests that there is consistent interest in this coin.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 5000 to 8000 euros, considering that the condition is good and that previous auction prices have been significantly higher.

Therefore, a reasonable estimated maximum purchase price could be between 6000 and 7000 euros.