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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in fairly good shape, but not the best possible condition.

2. Auction History:
- The average hammer price for similar coins in the past is 251.79 euros.
- The last auction for this coin had a hammer price of 380 euros, suggesting that there is considerable interest in this coin.
- In previous auctions, hammer prices have varied, but there are examples of sales exceeding 300 euros.

3. Starting Price: The starting price is 300 euros, indicating that the seller has high expectations for this auction.

4. Price Trends: Observing the hammer prices in previous auctions, it seems there is an increase in interest and value for this particular coin, especially in similar conditions.

Based on these factors, an estimated maximum purchase price could be in the range of 350 to 400 euros. This is because, although the starting price is 300 euros, the interest in the coin and previous hammer prices suggest it could reach a higher value at auction.

Therefore, a reasonable maximum purchase price could be approximately 400 euros.