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 of 75 (MBC). This is an important factor, as coins in better condition tend to reach higher prices.

2. Current Starting Price and Previous Prices: The current starting price is 300 euros. In previous auctions, coins with a similar condition (75) have had hammer prices that vary, but generally, hammer prices for condition 75 have been around 300 to 400 euros.

3. Average Hammer Price: The average hammer price for this reference is 553.38 euros. This suggests that, in general, coins of this reference tend to sell for a higher price than the starting price.

4. Historical Trends: Looking at the hammer prices of coins with a condition of 75 in the past, it can be seen that they have reached hammer prices of up to 400 euros on several occasions. However, there are also examples of coins with higher conditions that have reached significantly higher prices.

5. Demand and Supply: Since there are no scheduled auctions in the coming days for this coin, demand could be higher, which could increase the hammer price.

Based on these factors, an estimated maximum purchase price for this coin could be between 400 and 500 euros. This is because, although the starting price is 300 euros, the historical trend and average hammer price suggest that it could reach a higher price, especially if there is interest in the auction.

Therefore, a reasonable maximum purchase price could be 450 euros.