To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

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

2. Previous Auction Prices: By looking at the auction prices for coins with a similar condition (75) in the past, we can see that:
- In several auctions, the hammer prices for coins with a condition of 75 have ranged between 160 and 300 euros.
- For example, at the auction on 2020-10-21, a coin with a condition of 75 was sold for 300 euros.

3. Average Hammer Price: The average hammer price for this coin is 318.73 euros, suggesting that, in general, coins of this reference tend to sell for relatively high prices.

4. Starting Price: The current starting price is 150 euros, which is quite reasonable compared to previous hammer prices.

5. Recent Trends: In the most recent auctions, the hammer prices for coins with similar conditions have shown an increase, which could indicate a rising trend in interest for this coin.

Based on these factors, an estimated maximum purchase price for the coin could be around 300-350 euros, considering that this price reflects both the current condition and the previous hammer prices as well as market trends.