To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Starting price: 1800 euros.
2. Condition of the coin: 85 (ebc-), which is a good condition.
3. Historical data:
- The average starting price of similar coins is 2320 euros.
- The average hammer price is 2720 euros.
- In previous auctions, hammer prices have varied, but the highest was 4000 euros in 2014, although the condition of that coin is not specified.

Given that the condition of the current coin is 85, which is comparable to some of the conditions of the coins auctioned previously, we can make an estimation.

- The highest hammer price in the past for a similar condition was 3200 euros in 2019.
- Considering that the average hammer price is 2720 euros, and that the condition of the current coin is good, a hammer price in the range of 2500 to 3000 euros seems reasonable.

Therefore, an estimated maximum purchase price could be around 2800 euros. This is based on the trend of previous prices and the current condition of the coin.