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

1. Starting price: 1500 euros.
2. Current condition: 100 (S/C), indicating that the coin is in excellent condition.
3. Auction history: The coin has been auctioned once before, with a hammer price of 1500 euros and an estimated price of 3000 euros. The condition of that coin was 95, which is lower than the current condition.

Since the condition of the coin being auctioned now is better (100 compared to 95), and considering that the previous hammer price was 1500 euros, it is reasonable to assume that the price could be higher in this auction.

However, the starting price is 1500 euros, and given that there has been prior interest (it has sold in the past and has not gone unsold), this suggests that there is a market for this coin.

Estimated maximum purchase price:
- Given that the previous hammer price was 1500 euros and the current condition is better, we could estimate that the price could increase.
- A reasonable increase could be in the range of 20-30% over the previous hammer price, considering the condition.

Therefore, an estimated maximum purchase price could be in the range of 1800 to 1950 euros. This reflects an increase due to the better condition and interest in the coin, but it also remains within a reasonable range considering the starting price and auction history.