Based on the provided data, we can observe that the coin in question had an opening price in the current auction of 18 euros, with a grade of 80 (MBC+). Additionally, it has been auctioned in the past on several occasions, with closing prices ranging between 8 and 92 euros.

The average closing price of this coin in previous auctions has been 39.74 euros, with an average opening price of 36.3 euros. The grade of the coin in this auction is 80 (MBC+), indicating that it is in fairly good condition.

Considering this data, as well as the coin's previous price history, we could estimate a maximum purchase price around 50-60 euros. Given that the highest closing price was 92 euros in the past, and considering the current condition of the coin, an estimated maximum purchase price of 50-60 euros seems reasonable.