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 70 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Auction Prices: By observing the previous auction prices of coins with similar grades, we can see that there is a price trend that varies considerably. For example:
- A coin with a grade of 75 sold for 1125.97 and 537.97 in different auctions.
- A coin with a grade of 90 sold for 2500 and 5500 in other auctions.

3. Average Auction Price: The average auction price for this coin is 1484.65 euros, indicating that, in general, coins of this reference tend to sell for relatively high prices.

4. Starting Price: The starting price is 100 euros, suggesting that the auctioneer expects considerable interest in the coin.

5. Market Trends: Given that the coin has been auctioned 38 times in the past and has had a high sales percentage (35 out of 38), this indicates that there is an active market for this coin.

Based on these factors, an estimated maximum purchase price could be in the range of 800 to 1200 euros, considering that the grade is slightly lower than some coins that have reached higher prices, but it is still a desirable coin with a history of successful sales.

Therefore, a reasonable maximum purchase price could be 1000 euros.