To estimate a maximum purchase price for the coin in question, we can consider several factors:

1. Current Condition: The coin has a condition of 75 (MBC), which indicates that it is in fairly good shape, but not the best possible condition.

2. Auction History:
- The average hammer price in previous auctions is 57.66 euros.
- In past auctions, hammer prices for coins with similar conditions (75) have varied, but hammer prices of up to 95 euros have been seen for a condition of 80.

3. Price Trends:
- The estimated price in previous auctions for coins with conditions of 75 has been around 40 to 50 euros, with hammer prices reaching up to 55 euros.

4. Starting Price: The current starting price is 30 euros, which suggests that there is room for the hammer price to be higher.

Based on these factors, an estimated maximum purchase price could be in the range of 60 to 70 euros, considering that the coin is in good condition and that the price history shows that similar coins have reached higher prices in the past.

Therefore, a reasonable maximum purchase price could be 70 euros.