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

1. Starting price: 170 euros.
2. Current condition: 25 (BC), indicating a fairly low condition.
3. Auction history:
- In 2020, the coin was auctioned with a starting price of 150 euros and sold for 200 euros, with a condition of 70.
- In 2024, the starting price was 180 euros and it sold for 230 euros, also with a condition of 70.

Given that the current condition of the coin is significantly lower (25 vs. 70), this will negatively affect its value. Coins in better condition (condition 70) have reached auction prices of up to 230 euros.

To estimate a maximum purchase price, we can consider that, given the condition, the final price could be considerably lower. A reasonable approach would be to apply a significant discount based on the difference in condition.

If we take the highest final price of 230 euros and consider that a condition of 25 could justify a discount of 50-70%, we could estimate a maximum purchase price in the range of 70 to 115 euros.

However, since the starting price is 170 euros, and considering that the market may not be willing to pay more than what has been seen in the past for coins in worse condition, a reasonable maximum purchase price could be around 100 euros. This reflects a balance between the condition and the auction price history.