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

1. Current Condition: The coin has a condition of 75 (MBC), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price in previous auctions is 315.83 euros.
- The coin has been sold every time it has been auctioned, indicating a consistent interest in it.
- In previous auctions, hammer prices have varied, but there are examples of sales exceeding 400 euros, especially for coins with similar conditions.

3. Starting Price and Estimates:
- The current starting price is 300 euros, which is a good starting point.
- The average starting price in the past has been 211.36 euros, suggesting that the current starting price is relatively high, but not unusual for a coin in good condition.

4. Recent Trends: In the most recent auction, a coin with a condition of 80 sold for 600 euros, indicating that there is potential for price increases depending on demand.

Based on these factors, an estimated maximum purchase price could be between 400 and 450 euros. This is based on the historical interest in the coin, its good condition, and the price behavior in previous auctions. However, it is important to consider the competition in the auction and current demand, which could influence the final price.