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

1. Current Grade: The coin has a grade of 80 (MS+), indicating that it is in relatively good condition. This suggests that its value should be in the upper range of previous auction prices for coins of similar grade.

2. Previous Auction Prices: Looking at previous auction prices for coins with a grade of 80, we find that the average hammer price is approximately 129.68 euros. However, there have been auctions that reached higher prices, such as 250 euros in past sales.

3. Auction Trends: The coin has been auctioned 41 times, of which 38 have resulted in sales. This indicates a consistent interest in the coin, which may increase its market value.

4. Starting Price and Average Starting Price: The current starting price is 75 euros, which is below the average starting price of 79.34 euros. This could indicate an opportunity for buyers, as the starting price is lower than the average.

5. Price Estimates: In previous auctions, the estimated price for coins of similar grade has varied, but generally, hammer prices have exceeded starting prices. For example, in a recent auction, a coin with a grade of 80 sold for 85 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 150 and 200 euros. This is based on the fact that, although the starting price is 75 euros, the grade and interest in the coin suggest that it could reach a higher hammer price, especially if there is competition among bidders.

Therefore, a reasonable maximum purchase price could be 180 euros.