To estimate a maximum purchase price for the coin in question, let's consider several factors:

1. Starting Price: 400 euros, which is quite low compared to previous auction prices.
2. Condition: The coin has a condition of 75 (VF), which is lower than the 95 condition of previously auctioned coins. This suggests that its value may be less than that of coins in better condition.
3. Previous Prices: Previous auction prices for coins with a condition of 95 have been significantly higher (2700, 3200, and 2200 euros). However, since the condition of the current coin is lower, we need to adjust our expectations.
4. Average Auction Price: The average auction price for coins of this reference is 2145 euros, indicating a potential high value, but again, the condition affects this value.

Given that the condition of the current coin is 75, we could estimate that its value might be approximately 50-60% of the average auction price of coins in better condition.

Calculating 50% of the average auction price (2145 euros):
- 50% of 2145 = 1072.5 euros

Calculating 60% of the average auction price:
- 60% of 2145 = 1287 euros

Therefore, an estimated maximum purchase price for this coin, considering its condition and previous auction prices, could be between 1072 and 1287 euros.

Recommendation: A reasonable maximum purchase price could be around 1200 euros, taking into account the condition and the market context.