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

1. Starting price: 2500 euros.
2. Average past auction price: 3000 euros.
3. Current condition: 100 (MS), which is an excellent condition.
4. Auction history: The coin has been auctioned once before, with a hammer price of 3000 euros and a condition of 95.

Since the current condition is better (100 vs. 95), it is reasonable to assume that the hammer price could be higher than the previous 3000 euros. Additionally, the fact that there have been no failed sale attempts in the past suggests that there is interest in the coin.

Taking these factors into account, an estimated maximum purchase price could be between 3000 and 3500 euros, considering that the condition is better and that the interest in the coin seems to be positive.

Therefore, a reasonable maximum purchase price could be 3500 euros.