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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price in previous auctions is 55.93 euros.
- The coin has been auctioned 15 times, of which it has sold 14 times, indicating good demand.
- In recent auctions, hammer prices have reached up to 100 euros for coins of similar condition (for example, in the auction on 2022-09-14).

3. Starting Price and Average Starting Price:
- The current starting price is 30 euros, which is lower than the average starting price of 42.33 euros. This suggests that there is potential for the hammer price to be higher.

4. Price Trends:
- In recent auctions, hammer prices have varied, but there are examples of hammer prices exceeding 90 euros for coins of similar condition.

Based on these factors, an estimated maximum purchase price could be in the range of 80 to 100 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 90 euros.