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 of 80 (MBC+), indicating that it is in relatively good shape. This suggests that its value should be in the upper range of coins with similar conditions.

2. Previous Prices: Looking at previous auction prices for coins with similar conditions (80 and 85), we can see that:
- In 2020, a coin with a condition of 80 was auctioned for 150 euros.
- In 2020, another coin with a condition of 85 was auctioned for 180 euros.
- In 2022, a coin with a condition of 70 was auctioned for 130 euros.

3. Starting Price and Average Auction Price: The current starting price is 150 euros, and the average auction price in the past has been 145.11 euros. This indicates that the starting price is reasonable and that there is a possibility that the auction price could be similar or higher.

4. Auction Trends: The coin has been auctioned 12 times in the past, of which it has sold 10 times. This suggests that there is consistent interest in the coin, which may increase its value at auction.

5. Maximum Price Estimate: Given that the condition is 80 and considering previous auction prices, a reasonable maximum purchase price could be in the range of 180 to 200 euros, especially if there is interest in the auction.

Therefore, an estimated maximum purchase price for this coin could be 200 euros.