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

1. Current Condition: The coin has a condition rating of 95 (EBC+), indicating that it is in very good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for coins with a similar condition (95) in the past has been approximately 480 euros (considering auctions from 2020 and 2024).
- The last auction for a coin with a condition of 95 had a hammer price of 551 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 400 euros, which is higher than the average starting price of 271.17 euros. This suggests that there is an expectation for the coin to sell at a higher price.

4. Sales Trends: The coin has been sold in 29 out of 31 auctions, indicating good demand and sustained interest in this reference.

5. Comparison with Previous Prices:
- In previous auctions, coins with a condition of 95 have reached hammer prices ranging from 350 to 700 euros, showing a wide range depending on demand and other factors.

Based on these points, an estimated maximum purchase price for this coin could be between 500 and 600 euros, considering that the highest hammer price in the past for a coin of similar condition was 551 euros and that interest in this coin appears to be strong.

Therefore, a reasonable maximum purchase price could be 550 euros.