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 generally reduces its value compared to coins in better condition.

2. Historical Prices: By looking at previous auction prices for coins with a similar condition (30), we can see that the hammer prices have varied. For example, in previous auctions, the hammer prices for coins with a condition of 30 have ranged from 15 to 40 euros.

3. Average Hammer Price: The average hammer price for this coin is 98.02 euros, but this includes coins in better condition. Given that the condition of the coin in question is quite low, it is unlikely to reach that price.

4. Starting Price and Average Starting Price: The starting price is 15 euros, and the average starting price is 61.47 euros. This suggests that interest in the coin may be moderate, especially considering its condition.

5. Recent Trends: In the most recent auctions, the hammer prices for coins with similar conditions have been in the range of 20 to 35 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 25 and 35 euros. This reflects a balance between the current condition and historical prices, as well as market interest.

Therefore, a reasonable maximum purchase price could be 30 euros.