To estimate a maximum purchase price for the coin in question, let's consider the following factors:

1. Starting Price: 60 euros. This is the initial price set for the auction.
2. Auction History: The coin has been auctioned once before, with a starting price of 30 euros and a hammer price of 180 euros. This indicates that there is significant interest in this coin, despite its condition.
3. Condition: The coin has a condition rating of 30 (BC+), suggesting that it is not in the best condition, but it may still hold considerable value.
4. Average Hammer Price: The average hammer price for this coin in the past was 180 euros, indicating that, despite its condition, there is a market willing to pay a high price.

Given that the average hammer price is significantly higher than the current starting price, and considering that the coin has a history of successful sales, we could estimate that the maximum purchase price could be in a higher range.

Taking all these factors into account, an estimated maximum purchase price could be between 150 and 200 euros, given that the previous hammer price was 180 euros and the interest in the coin appears to be high. However, since the condition is not excellent, it is wise not to exceed 200 euros.

Therefore, a reasonable maximum purchase price could be 180 euros.