To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the current condition of the coin (75, VF) and the hammer prices of coins with similar conditions in previous auctions.

1. Current Condition: The coin has a condition of 75 (VF), indicating that it is in acceptable shape, but not of the highest quality.

2. Previous Hammer Prices: By observing the hammer prices of coins with similar conditions:
- In the auction on October 19, 2022, a coin with a condition of 75 was sold for 347 euros.
- In other auctions, coins with conditions of 70 and 80 have sold for between 160 and 440 euros.

3. Price Trends: The average hammer price for this particular coin is 422 euros, suggesting that, in general, coins of this reference tend to reach higher prices.

4. Starting Price and Average Starting Price: The current starting price is 300 euros, and the average starting price in the past has been 353.64 euros.

Based on this data, an estimated maximum purchase price for the coin could be in the range of 350 to 400 euros, considering that the condition is 75 and that the highest hammer price in the past for a similar condition was 347 euros.

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