Based on the provided data, we can observe that the coin in question has had varying starting and final prices in previous auctions, as well as different price estimates. The current condition of the coin is estimated at 30 (BC+).

Given that the average starting price is 34.09 euros and the average final price is 51.67 euros, we can see that historically auctions have exceeded the starting price in most cases.

Taking into account the previous prices of the coin and its current condition, as well as the fact that it has been sold in most previous auctions, we could estimate a maximum purchase price around 60-70 euros.

It is important to note that the final price in an auction can vary depending on the demand at that specific moment, so it is advisable to pay attention to the auction and adjust the offer accordingly.