To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Starting Price: 80 euros. This is the initial price set for the auction.
2. Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in good condition. This generally increases its value compared to coins of lower condition.
3. Auction History: The coin has been auctioned 2 times in the past, of which it sold 1 time and did not sell 1 time. This suggests that there is interest in the coin, but also that there may be limitations in demand.
4. Previous Prices: In the previous auction, the coin was offered with a starting price of 30 euros and sold for the same price. This indicates that the market has valued this coin in a lower range in the past.

Given that the current starting price is 80 euros and considering the condition and auction history, an estimated maximum purchase price could be in a range between the starting price and the average hammer price of previous auctions.

Taking all these factors into account, an estimated maximum purchase price could be approximately 70-90 euros. This allows for some margin for competition in the auction, but also considers the price history and the condition of the coin.