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 80 (MBC+), indicating that it is in relatively good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Current Listing Price and Previous Prices: The current listing price is 300 euros, and the average hammer price in previous auctions is 328.83 euros. This suggests that the hammer price tends to be close to the listing price, which is a good indicator.

3. Auction History: The coin has been auctioned 63 times, of which it has sold 49 times. This indicates good demand and consistent interest in the coin.

4. Previous Hammer Prices: In past auctions, hammer prices for coins with a similar condition (80) have varied, but there are examples of hammer prices reaching up to 650 euros (as seen in the March 2023 auction).

5. Price Trends: The average hammer price of 328.83 euros and the fact that there have been higher hammer prices in the past suggest that there is potential for the hammer price to exceed the current listing price.

Considering all these factors, an estimated maximum purchase price could be in the range of 400 to 600 euros, given that the condition is good and there is a history of hammer prices supporting this estimate.

Therefore, a reasonable maximum purchase price could be approximately 500 euros.