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 quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Auction Prices: By looking at previous auction prices, we can see that they have varied, but there are several examples of auctions that exceeded 80 euros, especially for coins in similar conditions (80 and 75 condition).

3. Average Auction Price: The average auction price for this coin is 71.67 euros, which gives us a good reference for what buyers are willing to pay.

4. Auction Trends: The coin has been auctioned 13 times, of which 12 have sold. This indicates a consistent interest in the coin, which may increase its value in the current auction.

5. Starting Price and Estimates: The starting price is 30 euros, and the average starting price is 33.58 euros. However, given that the condition is good and there is interest in the coin, it is reasonable to expect that the final auction price will be significantly higher.

Based on these factors, an estimated maximum purchase price could be in the range of 90 to 120 euros. This is based on the fact that in previous auctions, coins with similar conditions have reached final prices of up to 140 euros. Therefore, a prudent maximum purchase price could be 100 euros.