Based on the provided data, we can conduct an analysis to estimate a maximum purchase price for the coin in question.

1. Starting price: 6000 euros.
2. Average hammer price in the past: 7500 euros.
3. Condition of the coin: 100 (Uncirculated), indicating that it is in excellent condition.
4. Auction history: The coin has been auctioned once before, with a hammer price of 7500 euros.

Given that the coin has a high condition rating and has reached a hammer price of 7500 euros in the past, it is reasonable to consider that the hammer price could be similar or even higher in the next auction, especially if there is interest among collectors.

Estimation of the maximum purchase price:
- Considering the previous average hammer price (7500 euros) and the fact that the coin is in excellent condition, a maximum purchase price could be around 8000 euros. This allows for a margin for competition in the auction and the potential interest from other buyers.

Therefore, an estimated maximum purchase price for this coin could be 8000 euros.