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 rating of 75 (MBC), indicating that it is in quite good shape. This can positively influence its value.

2. Auction History:
- The average hammer price in previous auctions is 40.8 euros.
- The coin has been auctioned 11 times, of which it has sold 10 times, indicating good demand.
- Previous hammer prices for coins with similar conditions (75 and 80) have ranged between 30 and 95 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 20 euros, which is relatively low compared to the average hammer price of 40.8 euros.
- The average starting price is 35.17 euros, suggesting that the current starting price could be a good buying opportunity.

4. Price Trends:
- In previous auctions, hammer prices have varied, but there are examples of sales reaching up to 95 euros in similar conditions.

Based on these factors, an estimated maximum purchase price could be between 60 and 80 euros, considering that the condition is good and that the price history shows that similar coins have reached higher prices in the past.

Therefore, a reasonable maximum purchase price could be 75 euros.