Based on the provided data, the coin in question has a conservation grade of 75 (MBC) and has had starting and final prices in previous auctions. The starting price this time is 30 euros, and the average final price in previous auctions has been 34 euros.

Considering that the current starting price is 30 euros and the average final price in previous auctions has been 34 euros, we can see that historically auctions have exceeded the starting price. Additionally, the estimated price in previous auctions has ranged between 15 and 70 euros.

Given that the conservation grade of the coin is 75 (MBC), and taking into account the upward trend in final prices, as well as the range of estimated prices in previous auctions, my estimate for a maximum purchase price would be around 40-45 euros. This is considering that the current starting price is 30 euros and historically auctions have surpassed this price, reaching even up to 70 euros in the past.