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+), indicating that it is not in the best shape. This generally negatively affects the auction price.

2. Auction History:
- In 2019, a coin with the same condition (30) was auctioned with a final price of 280 euros, suggesting that there is a market willing to pay high prices for coins of this reference, even in less than optimal conditions.
- In 2020, the starting price was 90 euros, but it did not sell, indicating that interest may have fluctuated.
- In 2017, the final price was 120 euros, which is also relevant, although the condition of that coin is not specified.
- In 2014, the final price was 190 euros, showing that interest in this coin has varied over the years.

3. Starting Price and Average Final Price: The current starting price is 125 euros, and the average final price in previous auctions is 147.25 euros. This suggests that the final price could be in a similar range.

4. Market Trends: Since the coin has sold in all previous auctions and there have been no failed sale attempts, this indicates a consistent interest in the coin.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the condition is not optimal but there is a history of high prices in previous auctions. A price of 180 euros could be a good benchmark for a competitive offer, given the auction history and interest in the coin.