Based on the data provided, we can observe that the coin has had an average auction closing price of 64.27 euros in previous auctions. Additionally, the condition of this coin is graded at 75 (MBC).

Considering that the starting price in the upcoming auction is 18 euros and the estimated average closing price is 64.27 euros, we can assume that the closing price could be around that value or even slightly higher due to the trend observed in previous auctions.

Given that the condition of the coin is 75 (MBC), and taking into account previous closing prices, we could estimate a maximum purchase price of around 70-75 euros for this coin in the upcoming auction. It is important to note that this is just an estimate and the final price could vary depending on demand at the auction.