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 of 75 (MS), indicating that it is in fairly good shape, but not the best possible condition.

2. Historical Prices: Looking at previous auction prices for coins with a similar condition (75), we can see that they have varied. For example:
- In 2020, a coin with a condition of 75 was auctioned for 400 euros.
- In other auctions, hammer prices have ranged from 130 to 495 euros for similar conditions.

3. Average Hammer Price: The average hammer price for this coin is 353.51 euros, which gives us a good reference for what buyers are willing to pay.

4. Starting Price: The starting price is 175 euros, which is relatively low compared to previous hammer prices.

5. Sales Trends: The coin has been auctioned 81 times, of which 72 have been sold, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 350 to 450 euros, considering that the average hammer price is 353.51 euros and that there are examples of previous auctions exceeding 400 euros.

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