To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially considering the current grade of the coin (75, MS) and the auction prices of coins with similar grades in the past.

1. Grade and Historical Prices:
- A grade of 75 (MS) is quite good, and in the past, coins with similar grades have reached auction prices that varied significantly.
- By observing the auction prices of coins with grades from 70 to 80, we can see that the auction prices have ranged between 50 and 100 euros, depending on demand and other factors.

2. Auction Data:
- In several auctions, coins with a grade of 75 have reached auction prices of up to 110 euros.
- The average auction price for similar coins is approximately 101.29 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 40 euros, which is quite low compared to previous auction prices.
- The average starting price of 61.44 euros also suggests that there is potential for an increase in the auction price.

4. Maximum Price Estimation:
- Given that the grade is 75 and considering previous auction prices, a reasonable maximum purchase price could be in the range of 100 to 120 euros, as this aligns with the highest auction prices observed for coins of similar grade.

Conclusion: An estimated maximum purchase price for this coin could be 110 euros. This is based on the current grade and the historical auction prices of similar coins.