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

1. Current Condition: The coin has a grade of 25 (VG), indicating that it is in quite low condition. This will negatively affect its value compared to coins in better condition.

2. Historical Prices: Looking at previous auction prices, we can see that coins with higher grades (70 and 80) have reached hammer prices of up to 200 euros. However, the current coin has a significantly lower grade.

3. Starting Price and Average Price: The starting price is 180 euros, and the average hammer price in previous auctions is 179.17 euros. This suggests that the market is willing to pay close to this price, but given the condition, it is likely that the hammer price will be lower.

4. Sales Trends: The coin has sold in 6 of the last 7 auctions, indicating consistent interest, although the fact that there is a starting price higher than the average hammer price may suggest that buyers are cautious.

Given all this, and considering that the condition of the coin is quite low, an estimated maximum purchase price could be around 100-120 euros. This is based on the trend of previous hammer prices and the current condition of the coin.