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

1. Starting price: 1800 euros.
2. Average hammer price in the past: 2600 euros.
3. Condition of the coin: 95 (S/C-), indicating very good condition.
4. Estimated price in the previous auction: 3000 euros, although the hammer price was 2600 euros.

Given that the coin is in high condition (95) and has had a hammer price of 2600 euros in the past, it is reasonable to consider that the hammer price could be in a similar range or slightly higher in the next auction, especially if demand is high.

Considering that the starting price is 1800 euros and the previous average hammer price was 2600 euros, a maximum purchase price could be around 2800-3000 euros, taking into account that the hammer price may vary depending on the competition in the auction.

Therefore, an estimated maximum purchase price could be 3000 euros.