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 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:
- The average hammer price for this coin in the past has been 212.49 euros.
- Previous hammer prices for coins with similar conditions (75 and 90) have reached significantly higher figures, but the condition of 30 is considerably lower.

3. Starting Price: The current starting price is 25 euros, suggesting that the seller has moderate expectations for this auction.

4. Price Trends: Looking at previous hammer prices, even in higher condition grades, the lowest hammer price for similar conditions has been around 50-80 euros.

Given that the condition of this coin is quite low (30), and considering the price history, an estimated maximum purchase price could be in the range of 50 to 80 euros. This is based on the price trend for coins in similar conditions and the fact that the starting price is relatively low.

Therefore, an estimated maximum purchase price could be 70 euros.