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 (MBC+), which indicates that it is in quite good shape. This generally increases its value compared to coins with lower conditions.

2. Auction History:
- In 2013, a coin with a condition of 90 was auctioned with a starting price of 146.49 euros, although the final price is not known.
- In 2021, a coin with a condition of 75 had an unspecified starting price but sold for 52.64 euros.

3. Starting Prices and Average Prices:
- The current starting price is 50 euros, and the average starting price in the past has been 98.25 euros, with an average final price of 52.64 euros.

4. Demand and Supply: The coin has been auctioned 2 times in the past, of which it has sold 1 time. This suggests that there is moderate interest in the coin.

Given that the current condition of the coin is better than that of the 2021 auction and is close to that of 2013, we can infer that its value could be closer to the starting price of 146.49 euros for the coin with a condition of 90, although it will not reach that price due to the difference in condition.

Taking all these factors into account, an estimated maximum purchase price could be between 70 and 90 euros, considering that the condition is good and there is moderate interest in the coin. A price of 80 euros could be a reasonable starting point for an offer.