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

1. Coin 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 in lower condition.

2. Auction History:
- The average hammer price for this coin is 21.71 euros.
- In previous auctions, we have seen hammer prices that vary, but there are examples of sales reaching up to 65 euros (as seen in the auction on January 31, 2023).

3. Starting Price and Estimates:
- The current starting price is 15 euros, which is slightly higher than the average starting price of 11.06 euros.
- The estimated price for this auction is 30 euros, suggesting expectations for the coin to sell at a higher price.

4. Price Trends:
- In recent auctions, hammer prices have shown an increase, especially for coins in good condition.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 30 to 65 euros, considering that the highest recorded hammer price was 65 euros and the estimated price for this auction is 30 euros.

Therefore, a reasonable maximum purchase price could be between 30 and 40 euros. This allows for some margin for competition in the auction, given that the coin's condition is high and there is interest in it.