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

1. Current Condition: The coin has a condition rating of 70 (VF-), indicating that it is in quite good shape. This generally increases its value compared to coins with lower conditions.

2. Current Listing Price and Previous Prices: The current listing price is 75 euros, and the average hammer price in previous auctions is 65 euros. This suggests that the market has valued this coin in a similar range in the past.

3. Auction History: The coin has been auctioned 3 times and has sold in all of them, indicating a consistent interest in the coin. The highest hammer price in the past was 55 euros, although the estimated price in an auction was 30 euros.

4. Price Trends: The average listing price of 47.5 euros and the average hammer price of 65 euros suggest that there is potential for an increase in the hammer price, especially given that the current condition is better than in some of the previous auctions.

Taking all these factors into account, an estimated maximum purchase price could be around 90 euros. This is based on the good condition of the coin and the demonstrated interest in previous auctions, as well as the current listing price. However, it is important to consider that the final price will depend on the competition in the auction and the demand at that time.