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

The average starting price in previous auctions was 35.67 euros, while the average final price was 57.33 euros. The coin has been auctioned 15 times in the past, sold in 12 instances and unsold in 3 instances.

Considering the previous prices of the coin, its current condition, and the fact that it has sold in the majority of previous auctions, we could estimate a maximum purchase price around 60-70 euros. Given that the average final price has been 57.33 euros, a maximum purchase price in that range could be a prudent estimate.