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 75 (MBC), indicating that it is in quite good shape. This is important because coins in better condition tend to fetch higher prices.

2. Auction History:
- The coin has been auctioned 10 times and has sold on all those occasions, indicating good demand.
- The average hammer price in the past has been 76 euros, which can serve as a reference for the current price.
- In previous auctions, hammer prices have ranged from 37 euros to 280 euros, depending on the condition and other factors.

3. Starting Price and Average Starting Price: The current starting price is 50 euros, and the average starting price in the past has been 54.5 euros. This suggests that the current starting price is reasonable.

4. Recent Trends: In the 2022 auction, a coin with a condition rating of 85 sold for 280 euros, indicating that there is potential for high prices for good quality coins.

Given all this, and considering that the condition of the coin is 75, an estimated maximum purchase price could be in the range of 80 to 100 euros. This is based on the average hammer price and the price history of coins with similar conditions.

Therefore, an estimated maximum purchase price for this coin could be 90 euros.