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

1. 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 auction prices:
- In 2020, a similar coin with a condition of 70 was auctioned with a starting price of 110 and a final price of 190.
- In 2019, another coin with a condition of 70 had a starting price of 175 and a final price of 175.
- In 2014, a similar coin sold for 600, but there is no information about its condition.

3. Average final price: The average final price for similar coins is 301.25, but this is based on coins in better condition.

4. Current starting price: The starting price is 180 euros, which is lower than the average starting price of 198 euros.

Given that the condition of the coin is quite low (25), it is reasonable to assume that its value will be significantly affected. Based on previous final prices and the condition, an estimated maximum purchase price could be in a lower range.

Considering all these factors, an estimated maximum purchase price could be around 100-120 euros. This reflects the low condition and the fact that there have been previous auctions with higher final prices, but in much better conditions.