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 70 (MS-), which indicates that it is in an acceptable state, but not of the highest quality. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price in previous auctions is 165.49 euros.
- The last auction with a known hammer price was 190 euros for a coin with a condition of 80.
- Overall, hammer prices have varied, with some reaching up to 500 euros for higher conditions.

3. Starting Price: The current starting price is 150 euros, which may indicate the seller's expectations.

4. Sales Trends: Out of the 20 times it has been auctioned, it has sold 14 times, indicating a good sales rate. This suggests that there is demand for this coin.

5. Comparison with Previous Prices: Looking at previous hammer prices, the range has been quite broad, but the highest prices have been for coins in better conditions than the current one.

Taking all these factors into account, an estimated maximum purchase price could be around 180-200 euros. This is based on the average hammer price and the price trends for coins of similar condition. However, it is important to consider that the final price may vary depending on competition in the auction and the interest of other buyers.