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

1. Current Grade: The coin has a grade of 75 (MBC), indicating that it is in fairly good condition, but not among the highest qualities (FDC).

2. Previous Auction Prices: By observing the auction prices of coins with similar grades (around 70-80), we can see that:
- In 2019, a coin with a grade of 70 was auctioned for 40 euros.
- In 2021, a coin with a grade of 75 was auctioned for 44 euros.
- In 2022, a coin with a grade of 85 was auctioned for 190 euros, indicating a significant price jump with better condition.

3. Average Auction Price: The average auction price for this coin is 90.33 euros, suggesting that, in general, coins of this reference tend to reach higher prices.

4. Starting Price: The starting price is 25 euros, which is quite low compared to previous auction prices.

5. Estimation: Given that the grade is 75 and considering the previous auction prices, an estimated maximum purchase price could be between 50 and 70 euros. This is based on the fact that, although the grade is not the highest, the interest in the coin and the average auction price suggest it could reach a higher price.

Therefore, an estimated maximum purchase price for this coin could be between 60 and 70 euros.