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

1. Current Condition: The coin has a condition of 75 (MBC), which indicates that it is in relatively good shape, but it is not the best possible condition.

2. Historical Prices: By looking at previous auction prices, we can see that coins with similar conditions have had varying hammer prices. For example:
- In 2022, a coin with a condition of 80 was auctioned for 700 euros.
- In 2020, a coin with a condition of 70 was auctioned for 420 euros.
- In 2018, a coin with a condition of 85 was auctioned for 751 euros.

3. Average Hammer Price: The average hammer price for this coin is 944.38 euros, suggesting that, in general, coins of this reference tend to reach higher prices.

4. Starting Price: The current starting price is 350 euros, which is relatively low compared to previous hammer prices.

5. Sales Trends: Since this coin has sold in all previous auctions (13 out of 13), there is a consistent demand for it.

Based on these factors, an estimated maximum purchase price could be in a range that considers the current condition and previous hammer prices. Given that the condition is 75, a reasonable hammer price could be between 600 and 800 euros, considering that coins with similar conditions have reached those prices.

Therefore, an estimated maximum purchase price could be approximately 800 euros.