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

1. Condition: The coin has a condition rating of 95 (S/C-), indicating that it is in very good shape. This generally increases its value compared to coins with lower conditions.

2. Previous auction prices: By looking at the hammer prices from previous auctions for coins with a similar condition (95), we can see that the hammer prices have ranged from 261 to 420 euros.

3. Starting price and average prices: The current starting price is 400 euros, and the average hammer price in the past has been 294.35 euros. However, the average hammer price for coins in condition 95 has been higher, especially in recent auctions.

4. Recent trends: In the most recent auctions, the hammer prices for coins with condition 95 have been 340, 420, and 380 euros, suggesting an upward trend in the value of these coins.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 450 euros, considering that the starting price is 400 euros and there is a good chance that the hammer price will exceed this amount given the condition and recent trends.

Therefore, an estimated maximum purchase price could be 450 euros.