Based on the data provided, we can observe that the coin in question has had a starting price in the current auction of 40 euros, with a conservation grade of 70 (MBC-). Additionally, it has been auctioned in the past on several occasions, with closing prices ranging between 15 and 130 euros.

The average closing price of this coin in previous auctions has been 71.38 euros, with an average starting price of 41.82 euros. Considering the current conservation grade is 70 (MBC-), we can infer that the estimated purchase price could be in a range close to the previous closing prices.

Given that the current starting price is 40 euros and the average closing price has been 71.38 euros, we could estimate a maximum purchase price around 70-75 euros, considering the coin's conservation grade and previous closing prices. It is important to note that the value of a coin in an auction can vary depending on factors such as demand at that specific moment, so it is advisable to monitor the auction's progress to adjust the offer accordingly.