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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in relatively good shape, but not among the highest qualities.

2. Auction History:
- The average hammer price in previous auctions is 183.29 euros.
- The coin has been auctioned 18 times, of which it has sold 17 times, indicating good demand.
- In previous auctions, hammer prices have varied, but there are examples of sales reaching up to 420 euros in similar conditions (condition rating 85).

3. Starting Price and Estimates:
- The current starting price is 200 euros, which is slightly higher than the average starting price of 144.17 euros.
- The estimated price for this auction is 300 euros, suggesting expectations for the coin to reach a higher price.

4. Price Trends:
- In the most recent auctions, hammer prices have ranged from 255 to 300 euros for coins with similar conditions (condition rating 85).

Based on these factors, an estimated maximum purchase price could be in the range of 250 to 300 euros. This is because, although the condition is not the highest, demand and price history suggest it could reach a competitive price.

Therefore, a reasonable maximum purchase price could be approximately 280 euros.