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. Starting Price and Average Hammer Price: The current starting price is 1400 euros, and the average hammer price in previous auctions is 1007.32 euros. This suggests that the starting price is relatively high compared to what has been sold in the past.

3. Auction History: The coin has been auctioned 22 times and has sold on all those occasions. This indicates a consistent demand, which can influence the price.

4. Previous Prices: Looking at previous hammer prices for coins with similar grades (70 and 75), the hammer prices have ranged between 800 and 1350 euros. The highest hammer price for a grade of 70 was 1200 euros.

5. Recent Trends: In the most recent auction, the coin sold for 1500 euros with a grade of 75, indicating that there is potential for price increase depending on demand.

Based on these factors, an estimated maximum purchase price could be between 1200 and 1400 euros, considering that the starting price is 1400 euros and that the price history suggests it could reach up to 1350 euros at best. However, since the starting price is higher than the previous average hammer price, it may be prudent not to exceed 1300 euros to ensure a reasonable purchase.

Therefore, an estimated maximum purchase price could be 1300 euros.