Based on the provided data, we can observe that the coin in question had a starting price of 18 euros in the current auction, with a conservation grade of 70 (MBC-). Additionally, it has been auctioned in the past on eight occasions, always managing to sell.

The average starting price of previous auctions has been 21.29 euros, while the average final price has been 38.63 euros. The conservation grade of the coin in previous auctions has varied, with a conservation grade of 80 in one of the auctions.

Analyzing the previous prices of the coin, we can see that it has had a fairly wide price range, from 9 euros to 100 euros. The highest estimated price was 100 euros in a past auction.

Given that the coin has sold in all previous auctions and considering the observed price range, as well as the current conservation grade of 70 (MBC-), we could estimate a maximum purchase price of around 45-50 euros for this coin in the current auction. It is important to note that this is just an estimate and the final price may vary depending on demand and other factors in the auction.