Based on the data provided, we can observe that the coin in question has had a varied auction history in terms of starting prices, estimates, and final prices. The coin's condition has been maintained at an acceptable level, around 70 (VF+).

The starting price for the upcoming auction is 30 euros, with a historical average starting price of 114.74 euros, and an average final price of 156.81 euros. The coin has been auctioned 21 times in the past, sold in 16 instances and unsold in 5 instances.

Considering the coin's previous prices and its performance in past auctions, as well as its current condition, we could estimate a maximum purchase price around 150-200 euros. Given that the estimated prices in previous auctions have ranged between 60 and 400 euros, and considering the current starting price and auction history, a range of 150-200 euros could be a prudent estimate for the maximum purchase price on this occasion.