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

1. Current Condition: The coin has a condition of 30 (BC+), which indicates that it is not in the best shape. This will affect its value compared to coins in better condition.

2. Auction History: By looking at previous hammer prices for coins with similar conditions, we can see that the hammer price for coins in similar condition (30-40) has varied. For example, in previous auctions, coins with a condition of 30 have reached hammer prices of around 42-70 euros.

3. Starting Price and Average Hammer Price: The current starting price is 40 euros, and the average hammer price for this coin in the past has been 85.45 euros. However, since the current condition is lower, it is likely that the hammer price will not reach the average.

4. Recent Trends: In the most recent auctions, the hammer price for coins with similar conditions has been in the range of 50-80 euros.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 60-70 euros. This reflects a balance between the current condition and historical hammer prices, adjusted downward due to the condition of the coin.