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

1. Current Condition: The coin has a condition of 75 (MBC), which indicates that it is in quite good shape. This generally increases its value compared to coins of lower condition.

2. Auction History:
- In the past, this coin has been auctioned 4 times, of which it has sold 3 times. This suggests that there is interest in the coin, which may influence its price.
- Previous hammer prices are relevant. In the auctions of 2020 and 2022, the hammer prices were 25 and 60 euros, respectively, for conditions of 70. In the last auction, although the hammer price is unknown, the starting price was 70 euros with an estimated price of 110 euros.

3. Starting Price and Average Price: The current starting price is 50 euros, and the average starting price in the past has been 51.25 euros, with an average hammer price of 48.33 euros. This indicates that the market has valued this coin in a similar range in the past.

4. Price Trends: Given that the current condition of the coin is better than the previous ones (75 versus 70), it is reasonable to assume that the hammer price could be higher than the previous ones.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 70 to 90 euros, considering that the condition is better and that interest in the coin seems to be consistent. A price of 80 euros could be a reasonable starting point for an offer, as it is in the middle of this range and reflects an increase compared to previous hammer prices.