To estimate a maximum purchase price for the coin in question, we can analyze the provided data and consider several factors:

1. Condition: The coin has a condition rating of 75 (MBC), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- In the past, the coin has been auctioned 4 times and has sold on all occasions, indicating consistent interest in the coin.
- The previous hammer prices are:
- 240 € (2019)
- 360 € (2021)
- 240 € (2022)
- The average hammer price is 397.5 €, suggesting that, in general, buyers are willing to pay more than the starting price.

3. Current Starting Price: The starting price is 250 €, which is slightly higher than the starting price of some previous auctions, but still within a reasonable range.

4. Price Trends: The highest recorded hammer price is 360 €, indicating that there is potential for the coin to sell for a price above the starting price.

Given that the condition is good and considering the price history, an estimated maximum purchase price could be in the range of 360 € to 400 €. This is based on the highest previous hammer price and the consistent interest in the coin.

Therefore, an estimated maximum purchase price could be approximately 400 €.