To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Starting Price: 25 euros.
2. Condition: The coin has a condition rating of 80 (VF+), indicating that it is in quite good shape.
3. Auction History:
- It has been auctioned 4 times in the past, of which it has sold 2 times.
- The average hammer price in previous auctions is 25 euros.
- In 2016, it was auctioned with a starting price of 47.46 euros, although the final hammer price is unknown.

4. Average Starting Price: 29.15 euros, suggesting that the market has valued this coin slightly higher on other occasions.

Given that the condition is good and the average hammer price is equal to the current starting price, but considering that there have been past auctions with higher starting prices, we could estimate a maximum purchase price.

Taking all these factors into account, an estimated maximum purchase price could be between 30 and 35 euros, considering that the condition is favorable and the auction history shows interest in the coin.

Therefore, a reasonable maximum purchase price could be 35 euros.