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

1. Current Condition: The coin has a condition of 80 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Starting Price and Previous Prices: The current starting price is 75 euros, and the average hammer price in previous auctions is 84.01 euros. This suggests that the hammer price tends to be above the starting price.

3. Sales History: The coin has been auctioned 89 times, of which it has sold 85 times. This indicates high demand and good interest in the coin, which can influence the price.

4. Previous Hammer Prices: By looking at previous hammer prices for coins with similar conditions, we can see that prices have varied. For example, in previous auctions, coins with conditions ranging from 70 to 85 have reached hammer prices between 55 and 280 euros, depending on demand and other factors.

5. Recent Trends: In the most recent auctions, the hammer price has been as high as 240 euros for coins with similar conditions. This suggests that there is potential for the hammer price of this coin to be high.

Based on these factors, an estimated maximum purchase price could be in the range of 120 to 150 euros. This is based on the current condition, price history, and demand trend. However, it is important to note that the final price may vary depending on competition in the auction and other market factors at the time of sale.