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), indicating that it is in fairly good shape, but not among the best qualities.

2. Auction History:
- The average hammer price for similar coins in the past has been 37.61 euros.
- Previous auctions of coins with similar conditions (75-80) have had hammer prices that varied, but some examples are:
- 21 euros (2018-04-24)
- 30 euros (2022-06-28)
- 45 euros (2024-05-27)
- The trend shows that hammer prices can reach up to 60 euros in optimal conditions.

3. Starting Price and Average Starting Price:
- The current starting price is 18 euros, and the average starting price is 26.68 euros. This suggests that the market is willing to pay more than the starting price.

4. Demand and Supply:
- The coin has been auctioned 55 times in the past, with 29 sales, indicating moderate interest in the coin.

Based on these factors, an estimated maximum purchase price could be in the range of 40 to 60 euros, considering that the condition is good and that the price history shows that coins in similar conditions have reached hammer prices in that range.

Therefore, a reasonable estimated maximum purchase price could be 50 euros.