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

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

2. Auction History: By looking at previous auction prices for coins with similar grades, we can see that the highest hammer price for a coin with a grade of 30 was 33 euros. However, most hammer prices for higher grades (such as 70 and 80) are significantly higher.

3. Average Hammer Price: The average hammer price for this coin is 129.31 euros, but this includes coins in better condition. Given that the condition of the coin in question is quite low, it is unlikely to reach that price.

4. Recent Starting and Hammer Prices: In the most recent auctions, starting prices have been low (for example, a starting price of 12 euros with hammer prices of 20-25 euros for similar grades).

5. Market Trends: The coin has been auctioned 68 times, with a sell-through rate of 91% (62 out of 68). This suggests that there is consistent interest in the coin, which could help maintain its value.

Based on these factors, an estimated maximum purchase price for this coin, considering its condition and price history, could be between 25 and 35 euros. This reflects a balance between market interest and the condition of the coin.