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

1. Current Condition: The coin has a condition of 30 (BC+). This indicates that its state is not very good, which generally negatively affects its value.

2. Previous Prices: By observing the auction prices of coins with similar conditions (around 30), we can see that the auction prices have varied. For example, in previous auctions, coins with conditions of 30 have reached hammer prices between 50 and 70 euros.

3. Average Hammer Price: The average hammer price for this coin in the past has been 101.29 euros, but this includes coins in better conditions. Given that the current condition is lower, it is reasonable to adjust this value downward.

4. Starting Price: The current starting price is 30 euros, which may be a good indicator of the seller's expectations.

5. Market Trends: Since the coin has been auctioned 177 times and has had a good number of sales (151), this suggests that there is consistent interest in this coin, which can help maintain its value.

Based on these factors, an estimated maximum purchase price for this coin, considering its condition and previous hammer prices, could be between 50 and 70 euros. However, given that the condition is low, a more conservative price could be approximately 60 euros as a reasonable maximum purchase price.