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

1. Coin Condition: The coin has a condition rating of 75 (MBC), indicating that it is in relatively good shape. This suggests that its value should be above that of coins in worse conditions.

2. Auction History:
- The average hammer price for similar coins is 121.29 euros.
- In previous auctions, coins with similar conditions (75-85) have reached hammer prices that varied, but some examples are:
- 140 euros (2019-10-17) for a coin with a condition of 85.
- 200 euros (2020-10-21) for a coin with a condition of 85.
- 110 euros (2020-04-29) for a coin with an unspecified condition, but which sold above its starting price.

3. Starting Price and Previous Prices:
- The current starting price is 50 euros, which is below the average hammer price of similar coins.
- The average starting price of 61.84 euros also suggests that the current starting price is low.

4. Sales Trends: The coin has been sold in 35 out of 40 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the condition is good and that the auction price history for similar coins supports this estimate.

Therefore, a reasonable maximum purchase price could be 150 euros.