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

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

2. Auction History: The coin has been auctioned 37 times, of which it has sold 30 times. This indicates good demand and consistent interest in the coin.

3. Previous Prices: By looking at previous hammer prices for coins with similar conditions (75 and 80), we can see that hammer prices have varied. For example:
- In previous auctions, coins with a condition of 80 have reached hammer prices of up to 100 euros.
- The last auction with a condition of 75 had a hammer price of 90 euros.

4. Starting Price and Average Hammer Price: The current starting price is 50 euros, and the average hammer price in the past has been 44.43 euros. However, given that the condition is relatively good, it is reasonable to expect that the hammer price will be above average.

5. Price Trends: In recent auctions, hammer prices have shown an upward trend, especially for coins in good condition.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 90-100 euros, as this price reflects its condition and the interest demonstrated in previous auctions.