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

1. Current Condition: The coin has a condition of 75 (MBC), which is lower than some of the conditions of previously auctioned coins (80 and 85). This suggests that the hammer price could be lower compared to coins in better condition.

2. Previous Prices: Looking at the hammer prices of coins with similar conditions (75-80), the highest hammer price was 420 euros (for a condition of 80). However, it should be noted that the hammer price can vary depending on demand and other market factors.

3. Average Hammer Price: The average hammer price for this coin in the past has been 406.67 euros, which can serve as a good indicator of the expected value.

4. Current Starting Price: The starting price is 220 euros, which may attract more bidders, but also indicates that the seller has expectations of a lower price compared to the average hammer price.

5. Auction Trends: The coin has been auctioned 11 times, with an 81.8% sell-through rate, indicating a consistent interest in this coin.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 350 to 420 euros, considering that the condition is a limiting factor. A price of 400 euros could be a reasonable target, as it aligns with the average hammer price and the current condition of the coin.