Based on the provided data, the coin in question has a starting price of 18 euros and a conservation grade of 75 (MBC). In previous auctions, it has had closing prices ranging from 24 to 70 euros, with an average closing price of 48.8 euros.

Considering that the coin has been auctioned 5 times in the past and has always sold, and that the average starting price is 21.2 euros, we can estimate that the price of this coin tends to increase in auctions.

Given that the conservation grade of the coin is 75 (MBC), and taking into account the previous closing prices as well as the fact that it has sold in all previous auctions, we could estimate a maximum purchase price around 60-65 euros for this coin in the next auction.