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

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

2. Auction History:
- The average starting price from previous auctions is 36.01 euros, and the average hammer price is 49.88 euros.
- In the past, coins with a similar condition (75) have been auctioned, and the hammer prices have varied, with some reaching up to 180 euros in an auction.

3. Price Trends:
- The last auction for a coin with a condition of 85 had a hammer price of 55 euros, suggesting that the value may increase with better condition.
- The highest auction price for a condition of 75 was 180 euros, but that seems to be an exceptional case.

4. Current Starting Price: The starting price is 50 euros, indicating that the seller has reasonable price expectations.

Based on these factors, an estimated maximum purchase price could be in the range of 70 to 90 euros, considering that the condition is good and there is a price history that supports this estimate. However, since the starting price is 50 euros, it is likely that the hammer price will not significantly exceed this value unless there is active competition among bidders.

Therefore, a reasonable maximum purchase price could be 80 euros.