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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in a medium-low state. This generally affects the price, as coins in better condition tend to fetch higher prices.

2. Current Starting Price and Historical Prices: The current starting price is 150 euros, and the average starting price in previous auctions is 389.49 euros, with an average hammer price of 534.64 euros. This suggests that, in general, coins of this reference tend to sell for significantly higher prices than their starting price.

3. Sales History: The coin has been auctioned 97 times, of which it has sold 77 times. This indicates good demand and a history of successful sales.

4. Previous Hammer Prices: Looking at previous hammer prices for coins with a similar condition (75), we can see that they have reached hammer prices that vary, but some have been quite high (for example, 595.61 euros in 2012).

5. Recent Trends: In the most recent auctions, hammer prices have shown a trend of being higher, which could indicate an increase in demand or in the value of the coin.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 300 to 450 euros. This is based on the average hammer price of similar coins and the historical hammer price data for coins in similar conditions.

Therefore, a reasonable maximum purchase price could be approximately 400 euros.