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

1. Current Condition: The coin has a condition of 30 (BC+), which indicates that it is not in very good shape. This generally reduces its value compared to coins in better conditions.

2. Historical Prices: By looking at the auction prices of coins with similar conditions, we can see that the highest auction price for a condition of 30 was 120 euros in 2019. However, there are coins with higher conditions that have sold for significantly greater prices, suggesting that condition drastically affects the price.

3. Starting Price and Average Auction Price: The current starting price is 225 euros, and the average auction price for this coin in the past has been 364.14 euros. This suggests that there is potential for an increase in the auction price, but the condition must also be taken into account.

4. Market Trends: The coin has been auctioned 41 times, with an 87.8% sell-through rate, indicating a consistent interest in this coin. However, the current condition may limit collectors' interest.

5. Comparison with Prices of Similar Conditions: In the past, coins with similar conditions (30) have had auction prices ranging between 120 and 160 euros.

Taking all these factors into account, an estimated maximum purchase price for this coin, considering its condition and historical prices, could be around 150-180 euros. This would allow for a competitive offer without exceeding the value that collectors would be willing to pay for a coin in this condition.