Based on the provided data, the coin in question has a conservation grade of 70 (MBC-), with a starting price in the last auction of 30 euros and a final price of 45 euros. Considering that the average final price is 47.5 euros and that it was sold below this average price in the last auction, we could consider an estimated maximum purchase price slightly above the average final price.

Given that the conservation grade of the coin is 70 (MBC-), which is a medium conservation grade, and that it has performed well in previous auctions, we could estimate a maximum purchase price around 50-55 euros. It is important to note that this is just an estimate and the final price will depend on factors such as demand at the time of the auction and the willingness of buyers to bid on the coin.