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

1. Starting price: 1800 euros.
2. Average hammer price in previous auctions: 1900 euros.
3. Condition of the coin: 85 (ebc-), indicating good preservation.
4. Auction history: It has been auctioned 2 times, with 1 sale and 1 no sale. This suggests there is interest, but also that there may be a limit to what buyers are willing to pay.
5. Estimated price in the previous auction: 3000 euros, although the hammer price was 1900 euros.

Given that the average hammer price has been 1900 euros and considering that the condition is good (85), a reasonable maximum purchase price could be in the range of 2000 to 2200 euros. This is based on the fact that buyers may be willing to pay a little more than the previous average hammer price, especially if the condition is a positive factor.

Therefore, an estimated maximum purchase price could be 2100 euros.