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

1. Coin Condition: The coin has a condition rating of 30 (BC+), which indicates that it is not in the best condition. This will affect its value compared to coins in better condition.

2. Auction History: By observing the hammer prices of coins with a similar condition, we can see that the average hammer price for coins in similar conditions (BC+) has varied. For example, in previous auctions, coins with a condition of 30 have reached hammer prices of up to 50 euros.

3. Average Hammer Price: The average hammer price for this particular coin has been 100.37 euros, but this includes coins in better condition. Given that the condition of this coin is lower, it is reasonable to adjust this value downward.

4. Recent Starting and Hammer Prices: The current starting price is 50 euros, and in recent auctions, coins with similar conditions have had hammer prices ranging between 40 and 60 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 50 and 70 euros, considering that the condition limits its appeal to collectors. A price of 60 euros could be a reasonable benchmark, as it falls in the middle of this range and reflects buyer interest in coins of similar condition.