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

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

2. Historical Prices: By looking at previous auction prices for coins with similar conditions, we can see that:
- In recent auctions, coins with a condition of 80 have reached hammer prices of up to 200 euros.
- The average hammer price for coins of similar condition seems to be around 180-200 euros.

3. Starting Price and Average Hammer Price: The current starting price is 90 euros, and the average hammer price in the past has been 182.12 euros. This suggests that the hammer price could be significantly higher than the starting price.

4. Auction Trends: The coin has been auctioned 27 times, with a high percentage of sales (25 out of 27). This indicates a consistent interest in this coin, which may increase its value at auction.

5. Comparison with Previous Prices: In previous auctions, coins with conditions of 70 and 75 have reached hammer prices of up to 200 euros. Given that this coin has a better condition (80), it is reasonable to expect its hammer price to exceed those values.

Based on these factors, an estimated maximum purchase price for this coin could be between 200 and 250 euros, considering that the interest in the coin and its condition are favorable. However, given market behavior and price trends, a hammer price of around 220 euros could be a reasonable target.