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

1. Current Condition: The coin has a condition rating of 25 (BC), indicating that it is not in the best shape. This will affect its value compared to coins in better condition.

2. Auction History:
- In 2014, the coin was auctioned with a starting price of 125 euros and a final price of 150 euros.
- In 2022, the starting price was 150 euros, with a final price also of 150 euros. In this case, the condition was the same (25).

3. Average Starting and Final Prices: The average starting price is 137.5 euros and the average final price is 150 euros. This suggests that, in general, the coin has sold in a similar range in the past.

Given that the condition is low (25), it is likely that the final price will not significantly exceed 150 euros, which is the highest price reached in previous auctions for this condition.

Estimated Maximum Purchase Price: Considering all these factors, a reasonable maximum purchase price could be between 150 and 160 euros, given that the highest final price in the past was 150 euros and the estimated price in the previous auction was 160 euros. However, given the condition, a more conservative price could be around 150 euros.

Therefore, an estimated maximum purchase price could be 150 euros.