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

1. Current Condition: The coin has a condition rating of 75 (MBC), which indicates that it is in acceptable shape, but not in the best condition. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price in previous auctions is 447.95 euros, which gives us an idea of the value collectors are willing to pay.
- In the past, hammer prices have varied significantly, ranging from 90 euros to 1270.64 euros, depending on the condition and other factors.

3. Starting Price: The current starting price is 150 euros, which is significantly lower than the average hammer price.

4. Sales Trends: Out of the 9 times it has been auctioned, 8 have been sold, indicating a consistent interest in the coin.

5. Comparison with Previous Prices:
- In previous auctions, coins with a similar condition (75) have reached hammer prices of up to 650 euros.
- The last auction with a condition of 75 had a hammer price of 90 euros, suggesting that interest may have fluctuated.

Based on this data, an estimated maximum purchase price could be set in a range between 300 and 450 euros, considering that the average hammer price is 447.95 euros and that the current condition is 75.

Therefore, a reasonable maximum purchase price could be 450 euros.