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), which indicates that it is in fairly good shape, but not among the best qualities (FDC).

2. Historical Prices: By looking at previous auction prices for coins with similar conditions, we can see that auction prices have varied. For example:
- In recent auctions, coins with a condition of 90 and 95 have reached hammer prices of up to 440 euros.
- The last auction of a coin with a condition of 95 had a hammer price of 550 euros.

3. Starting Price and Average Price: The current starting price is 450 euros, and the average hammer price in the past has been 327.23 euros. This suggests that the starting price is relatively high compared to the historical average.

4. Market Trends: The coin has been auctioned 45 times, with a sell-through rate of 91.1% (41 out of 45). This indicates a consistent interest in this coin.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 500 euros, considering that the condition is not the highest and that the starting price is 450 euros.

Therefore, a reasonable maximum purchase price could be 450 euros, as it matches the starting price and reflects the interest in the coin, but does not exceed the hammer price of coins in better condition.