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

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

2. Previous Auction Prices: By observing the previous auction prices of coins with similar conditions, we can see that:
- In 2018, a coin with a condition of 85 was auctioned for 235 euros.
- In 2018, a coin with a condition of 70 was auctioned for 70 euros.
- In 2023, a coin with a condition of 80 was auctioned for 220 euros.

3. Price Trends: The average auction price for this coin has been 86.08 euros, which is also an important indicator.

4. Starting Price: The starting price is 50 euros, suggesting that the auctioneer expects interest in the coin.

5. Comparison with Estimated Prices: The estimated price for this coin in previous auctions has varied, but it has reached up to 300 euros in the case of coins in better condition.

Given that the condition of the coin is 75 (MBC), which is quite good, and considering the previous auction prices and the average auction price, an estimated maximum purchase price could be in the range of 150 to 200 euros. This is based on the price trends of coins with similar conditions and the interest it might generate at the auction.

Therefore, an estimated maximum purchase price for this coin could be approximately 180 euros.