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 30 (BC+), which indicates that it is not in the best condition. This will affect its value compared to coins in better condition.

2. Auction History: By observing previous hammer prices for coins with a similar condition (30), we can see that the hammer price has varied. For example:
- In the auction on November 19, 2020, a coin with a condition of 30 was sold for 35 euros.
- In the auction on July 2, 2020, another coin with the same condition was sold for 60 euros.

3. Average Hammer Price: The average hammer price for this coin in the past has been 103.53 euros, but this includes coins in better conditions.

4. Starting Price: The current starting price is 25 euros, which may indicate that the seller expects moderate interest.

5. Price Trends: In recent auctions, hammer prices have shown a trend of being higher, especially for coins with superior conditions.

Taking all these factors into account, an estimated maximum purchase price for this coin, considering its condition and auction history, could be between 40 and 60 euros. This is based on the fact that, although the condition is not high, there are precedents for sales in that range for similar coins.

Therefore, a reasonable estimated maximum purchase price could be 60 euros.