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), indicating that it is in quite good shape. This generally translates to a higher price compared to coins in lower condition.

2. Auction History:
- The average hammer price for coins of similar condition (75) in the past has been 20 (2020-09-17) and 24 (2018-10-15).
- There is also a recent auction of 90 (2023-01-31) for a coin in condition 80, suggesting that the market is willing to pay more for coins in good condition.

3. Average Starting and Hammer Price:
- The average starting price is 39.82 and the average hammer price is 52.91. This indicates that, in general, coins of this reference tend to sell above their starting price.

4. Recent Trends:
- In the most recent auction, the coin sold for 90, suggesting that there is growing interest in this reference.

5. Comparison with Previous Prices:
- The auction on 2022-04-28 shows a hammer price of 220 for a coin in condition 95, indicating that there is significant potential for value increase depending on the condition.

Based on these factors, an estimated maximum purchase price for the coin in condition 75 could be in the range of 70 to 90 euros. This is based on the recent interest in the coin and the hammer price history for coins of similar condition.