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 25 (BC), which indicates that it is in quite poor condition. This will negatively affect its value compared to coins in better condition.

2. Previous Prices: Looking at previous auction prices, we can see that:
- In 2020, a coin with a condition of 30 sold for 180 euros.
- In 2021, another coin with a condition of 30 also sold for 180 euros.
- In 2022, a coin with a condition of 70 sold for 200 euros.
- In 2023, a coin with a condition of 70 sold for 255 euros.
- In 2023, a coin with a condition of 95 sold for 2500 euros.

3. Starting Price and Average Price: The current starting price is 180 euros, and the average auction price in the past has been 582.5 euros. However, given that the current coin's condition is quite low, it is unlikely to reach prices close to the average.

4. Price Trends: The trend shows that coins in better condition (conditions 70 and 95) have reached significantly higher prices. However, the coin in question has a condition of 25, which limits its appeal to collectors.

Taking all these factors into account, an estimated maximum purchase price for this coin could be in the range of 150 to 200 euros, considering that condition is a critical factor and that previous auction prices for coins in similar conditions have been lower.

Therefore, a reasonable maximum purchase price could be 200 euros.